North Branch Water and Light
Wellhead Protection Plan
Part 1:
Delineation of the Wellhead Protection Area (WHPA),
Drinking Water Supply Management Area (DWSMA) and
Assessments of Well and DWSMA Vulnerability
Prepared for:
North Branch Water and Light
August, 2012
North Branch Water and Light Wellhead Protection Plan
Part I
Delineation of the Wellhead Protection Area (WHPA), Drinking Water Supply Management
Area (DWSMA) and Assessments of Well and DWSMA Vulnerability
August 2012
I hereby certify that this plan, document, or report was prepared by me or under my direct
supervision and that I am a duly Licensed Professional Geologist under the laws of the state of
Minnesota.
Signature:
John C. Greer
Date: August 7, 2012 Reg. No. 30347
Wellhead Protection Plan for North Branch Water and Light
Part I
Table of Contents
1.0
Introduction ................................................................................................................................. 1
2.0
2.1
2.2
2.3
2.4
2.5
2.6
3.0
3.1
3.2
3.3
Criteria for Wellhead Protection Area Delineation ..................................................................... 2
Time of Travel ............................................................................................................................ 2
Aquifer Transmissivity ............................................................................................................... 2
Daily Volume of Water Pumped ................................................................................................. 2
Conceptual Hydrogeologic Model .............................................................................................. 3
2.4.1 Geologic History ............................................................................................................ 3
2.4.2 Regional Bedrock Geology ............................................................................................ 3
2.4.3 Recharge and Discharge of Groundwater ...................................................................... 5
2.4.4 Direction of Groundwater Flow ..................................................................................... 5
Model Description ...................................................................................................................... 5
Groundwater Flow Field ............................................................................................................. 7
Delineation of the Wellhead Protection Area ............................................................................. 8
Porous Media Flow Evaluation ................................................................................................... 8
3.1.1 Sensitivity Analysis ....................................................................................................... 8
Fracture Flow Evaluation ............................................................................................................ 9
Other Groundwater Withdrawal.................................................................................................. 9
4.0
Delineation of the Drinking Water Supply Management Areas ............................................... 11
5.0
Well Vulnerability Assessment ................................................................................................. 12
6.0
Drinking Water Supply Management Area Vulnerability Assessment .................................... 13
7.0
Supporting Data Files ............................................................................................................... 14
8.0
References ................................................................................................................................. 15
Tables
Figures
Appendices
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List of Tables
Table 1 Data Elements
Table 2 Annual and Projected Pumping Rates for Mounds View Wells
List of Figures
Figure 1
Bedrock Geology
Figure 2
Geologic Cross Section A-A’
Figure 3
Geologic Cross Section B-B’
Figure 4
Geologic Cross Section C-C’
Figure 5
Well Capture Zones
Figure 6
WHPA & DWSMA
List of Appendices
Appendix A
Well Construction Records
Appendix B
Aquifer Test Data and Analysis
Appendix C
MDH Well Vulnerability Assessments
Appendix D
Summary of Fracture Flow Capture Zone Calculations
Appendix E
Groundwater Model
Appendix F
L-Score Map
Appendix G
Groundwater Model Files and GIS Shapefiles
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1.0 Introduction
Wellhead protection areas (WHPAs) and a Drinking Water Supply Management Area (DWSMA)
were delineated for North Branch Municipal Water and Light (NBWL). This report summarizes the
delineation of WHPAs and the DWSMA for NBWL as required by the Minnesota Wellhead
Protection Rules.
NBWL has six municipal water supply wells including Well 1 (unique number 217922), Well 2
(unique number 112244), Well 3 (unique number 522767), Well 4 (unique number 706844), Well 5
(unique number 749383), and Well 6 (unique number 593584). Wells 1, 2, and 6 pump water from
the Middle Proterozoic sedimentary aquifer and the Mount Simon – Hinckley aquifer. Well 3 and
Well 5 pump water from the Mount Simon–Hinckley aquifer. Well 4 pumps from a buried
Quaternary sand and gravel aquifer. Well locations are shown on Figure 1 and well construction data
are presented in Appendix A.
Data elements used in preparation of the report are presented in Table 1.
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2.0 Criteria for Wellhead Protection Area Delineation
The following criteria were used to ensure accurate delineation of the WHPA.
2.1
Time of Travel
A minimum ten-year time of travel criteria must be used to determine a WHPA
(MN Rule 4720.5510) so there is sufficient reaction time to remediate potential health impacts in the
event of contamination of the aquifer. A time of travel of ten years was considered in this study. As
required by the Wellhead Protection Rules, the one-year time of travel was also determined for each
well addressed in this study.
2.2
Aquifer Transmissivity
Per discussions with Minnesota Department of Health (MDH) staff during the Pre-Delineation
Meeting (MDH, 2011a), aquifer transmissivity and hydraulic conductivity were determined
as follows: 1) For the Mt. Simon – Hinckley aquifer a pumping test at NBWL Well 5 was used
(Appendix B). Based on this test, the transmissivity was estimated to be 5,370 ft 2/day; using
an aquifer thickness of 150 feet results in an estimated hydraulic conductivity of 35.8 ft/day
(10.9 m/day). 2) The aquifer transmissivity of the Middle Proterozoic sedimentary aquifer was
determined using a specific capacity test for NBWL Well 2 (Appendix B). Using the TGuess Method
(Bradbury and Rothschild, 1985), the transmissivity of the Middle Proterozoic sedimentary aquifer is
estimated to be 441 ft2/day and the hydraulic conductivity is estimated to be 4.4 ft/day (1.3 m/day).
3) The aquifer transmissivity for the Quaternary sand and gravel aquifer was determined using a
specific capacity test for NBWL Well 4. Using the Tguess Method the transmissivity of the
Quaternary aquifer is estimated to be 1,728 ft 2/day, and the hydraulic conductivity is estimated to be
29 ft/day (8.8 m/day). This falls within the expected range based on regional data from the
Minnesota Geological Survey and Metropolitan Council (Tipping et al., 2010) which indicates that
the hydraulic conductivity of Quaternary aquifers in the North Branch area range from 4.6 ft/day to
221.4 ft/day with a geometric mean hydraulic conductivity of 20.3 ft/day (n=89).
2.3
Daily Volume of Water Pumped
Pumping data for NBWL for the period 2006 through 2010 is summarized in Table 2. The largest
annual withdrawal for 2006-2010 was 239,353,000 gallons in 2007. The projected total withdrawal
for 2015 is estimated to be 292,700,000 gallons. Projected pumping rates for 2015 were estimated
for each well based on the percentage of the total volume that each well pumped from 2006-2010.
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The pumping rate for Well 6 was adjusted based on an estimated total use of 21 Mgal/yr (17Mgal/yr
for irrigation and 4 Mgal/yr for municipal peak demand) (Bonin, 2011). The pumping rates used for
W in the delineation of the WHPA were the maximum of either the projected 2015 pumping rate, or
those reported for 2006-2010. Table 2 summarizes the historical and projected distribution of the
annual withdrawal among the NBWL municipal wells and the pumping rates used for delineation of
the WHPA.
2.4
Conceptual Hydrogeologic Model
The conceptual hydrogeologic model is described in Barr (2005) and is repeated here with slight
modifications for completeness.
2.4.1 Geologic History
North Branch is located in the northern part of a geologic feature called the Hollandale Embayment –
a large bay in an ancient shallow sea were sediment was deposited as the seas waxed and waned to
form what is now most of the major bedrock geologic units in eastern Minnesota. Before the
deposition of what is now the Mt. Simon Sandstone, there was structural uplifting of Precambrian
rocks that formed an uplifted block (called a “horst”) that trends north-south. The western edge of
this horst corresponds approximately with Interstate 35. Subsequent tectonic activities formed a
structural basin (the Twin Cities basin), centered under what is now Minneapolis and St. Paul.
Bedrock units generally dip southward toward the center of the Twin Cities basin. There may have
been some reactivation of the Precambrian faults after deposition of younger rocks (Morey, 1972).
During the Quaternary (about the last two-million years), glacial advances eroded away higher relief
bedrock units and deposited a mixture of glacially derived tills and outwash over the landscape. The
combination of depositional history, structural faulting, and glaciation has resulted in the current
geologic setting. Major bedrock aquifer units, such as the Prairie du Chien-Jordan aquifer, are not
present in the North Branch area due to these processes. The Wonewoc Sandstone-Tunnel City Group
aquifer is present to the west of North Branch but underneath North Branch (where the underlying
horst feature is present), the uppermost bedrock unit is primarily the Mt. Simon Sandstone (and the
upper portion of this unit has also been eroded).
2.4.2 Regional Bedrock Geology
The bedrock geology as interpreted by Runkel and Boerboom (2010) is shown on Figure 1. Locations
of three geologic cross sections through the study area are also shown on Figure 1. Geologic cross
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section A-A’ is a west to east cross section (Figure 2); cross section B-B’ (Figure 3) and C-C’
(Figure 4) are north to south cross sections.
The hydrostratigraphic units of importance for this study are described in more detail below.
Chengwatana volcanics
The Chengwantana volcanics consist of deeply dipping sequences of interlayered ophitic to weakly
porphyritic basalt flows and coarse interflow conglomerate units. The western margin of this unit is
juxtaposed against the Mt Simon-Hinckley sandstone along the Douglas Fault in the vicinity of North
Branch (Runkel and Boerboom, 2010).
Mesoproterozoic Sedimentary Rocks
Mesoproterozoic sedimentary rocks consist of feldspathic sandstone, reddish-brown mudstone and
siltstone, and minor shale units of the Keweenawan Supergroup (Runkel and Boerboom, 2010). Due
to a limited number of borings and complexities associated with faulting in the area these units
cannot be assigned to individual formations but are likely related to the Solar Church and/or Fond du
Lac Formations. Of importance to this study is the informally defined St. Croix Horst Sandstone.
This sandstone is present below most of North Branch with bedding that dips 50o to 70o from
horizontal and is often cut by numerous thin, white veins of calcite (Boerboom, 2010).
Mt. Simon Sandstone
The Cambrian-aged Mt. Simon Sandstone consists of multiple beds of moderately-sorted to
well-sorted quartz sandstone intermixed with thin beds of feldspathic sandstone, siltstone, and shale
(Mossler and Tipping, 2000). The formation can be up to 250 feet thick in Chisago County (Runkel
and Boerboom, 2010). East of the Douglas Fault the Mt. Simon Sandstone is often the uppermost
bedrock. West of the Douglas Fault the Mt. Simon Sandstone is overlain by the Eau Claire
Formation (a confining unit) and the Wonewoc Sandstone and Tunnel City Group.
Eau Claire Formation
The Cambrian-aged Eau Claire Formation is a siltstone, very fine feldspathic sandstone, and
greenish-gray shale. Some sandstone beds are glauconitic. (Mossler and Tipping, 2000). The Eau
Claire Formation gradually coarsens to the north in Chisago County and is dominantly a very fine - to
fine-grained sandstone in the northern one-half of the county (Runkel and Boerboom, 2010).
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Wonewoc Sandstone
The Cambrian-aged Wonewoc Sandstone is medium to very coarse-grained, quartzose sandstone and
very-fine to fine-grained feldspathic sandstone, with scattered thin beds of shale (Mossler and
Tipping, 2000).
Tunnel City Group
The Cambrian-aged Tunnel City Group is divided into two formations: the Mazomanie Formation
and the Lone Rock Formation. The Mazomanie Formation is mostly a medium-grained friable,
quartz sandstone. The Lone Rock Formation underlies the Mazomanie Formation and consists of
fine grained glauconitic, feldspathic sandstone and siltstone (Runkel and Boerboom, 2010).
2.4.3 Recharge and Discharge of Groundwater
The primary mechanisms of recharge to the aquifer system in the region is infiltrating precipitation
that moves below the root zone of plants and migrates downward by gravity to the water table.
Recharge rates in east-central Minnesota are typically in the range of less than 1 inch per year to over
12 inches per year. A secondary source of recharge is seepage through the bottoms of lakes,
wetlands, and some streams. Water supplying individual aquifers which NBWL wells tap is
controlled by leakage from overlying confining units; either Quaternary clays, or the Eau Claire
Formation where present.
Most groundwater flows southeast and east toward the St. Croix River, which is a regional discharge
zone. Secondary discharge zones include smaller streams, some lakes and wetlands,
evapotranspiration from plants, and wells.
2.4.4 Direction of Groundwater Flow
Regional groundwater flow for all bedrock aquifers is to the east and south, toward the St. Croix
River. Differing directions of flow can be expected for the shallow aquifer (surficial deposits) near
lakes and streams. Near high capacity wells, groundwater flow is typically toward the wells.
2.5
Model Description
To accurately delineate the WHPA, it is necessary to assess how nearby wells, rivers, lakes, and
variations in geologic conditions affect groundwater flow directions and velocities in the aquifer.
The finite difference code MODFLOW-96 (McDonald and Harbaugh, 1988; Harbaugh and
McDonald, 1996) was used for this study to simulate groundwater flow in the hydrostratigraphic
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units from the Quaternary aquifer down to the Mesoproterozoic sedimentary rocks. MODFLOW is
public domain software that is available at no cost from the United States Geological Survey. The
pre- and post-processor Groundwater Vistas (version 6) (Environmental Simulations, Inc., 2011) was
used to create the data files and evaluate the results.
The base finite difference model used in this study is the groundwater flow model developed for
evaluation of future well locations for NBWL (Barr, 2005). Full description of this model is
presented in Appendix E. A brief summary and discussion of changes made to the model for this
project are presented below.
The groundwater flow model is a 5 layer model and includes all major hydrostratigraphic units in the
North Branch Area. The model layers generally correspond to the following: Layer 1 – Quaternary
sediments; Layer 2 – Tunnel City Group and Wonewoc Sandstone; Layer 3 – Eau Claire Formation;
Layer 4 – Mt. Simon Sandstone; and Layer 5 – Proterozoic Sediments. In the North Branch area,
where upper bedrock units are not present, the layers are represented as the Quaternary sediments.
The model takes into account regional flow boundaries. The major flow boundary near North Branch
is the St Croix River. To the west the model extends to the approximate extent of the Mt. SimonHinckley aquifer. Smaller streams and area lakes are also included in the model using constant head
cells and the River Package of MODFLOW. In addition, high capacity pumping wells from the State
Water Use Database System (SWUDS) are included in the model.
The model was modified in the vicinity of North Branch to better represent the local conditions.
Changes made to the model for use in delineating the NBWL WHPAs included:

Refining the model grid around NBWL municipal wells to a cell size of 10m x 10m;

Modify the hydraulic conductivity zones and layer elevations to match recently mapped
geology in the North Branch area (Boerboom, 2010; Runkel and Boerboom, 2010)

Adjust the location of the faults in the North Branch area based on recently mapped geology
(Runkel and Boerboom, 2010).

Hydraulic conductivity values of the Mt. Simon-Hinckley aquifer, and Proterozic sediments
adjusted based on values presented in Section 2.2.

Incorporate a new hydraulic conductivity zone in model layer 5 to represent the Proterozoic
sediments in an area of approximately 4 km2 around NBWL Wells 1 and 2.

Incorporate a new hydraulic conductivity zone to represent the Chengwantana volcanics .
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
Incorporate a new hydraulic conductivity zone to represent the buried sand and gravel aquifer
supplying Well 4. Review of Quaternary stratigraphy data indicated that this unit is
consistent with unit qsx as mapped by Meyer (2010).

Layer thicknesses to the west of North Branch in the vicinity of Isanti were adjusted based on
updated information.
After these revisions were made to the model a check on model calibration to hydraulic heads was
made. Calibration residuals for hydraulic head are presented in Appendix E.
Sensitivity of the model parameters was also evaluated and results are presented in Appendix E.
MODFLOW files for the calibrated model are included in Appendix G.
2.6
Groundwater Flow Field
Groundwater flow in the glacial aquifer and bedrock aquifers in the vicinity of North Branch is to the
east toward the St. Croix River. The ambient direction of groundwater flow was estimated based on
static water level data from well records obtained from the County Well Index. This flow direction is
consistent with the flow direction determined using the groundwater flow model in this study.
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3.0 Delineation of the Wellhead Protection Area
Delineation of the WHPA for the NBWL wells involved the evaluation of both porous media and
fracture flow. First, the capture zones for each well were delineated based on porous media flow and
then, because of extensive faulting in the area, the capture zones were also delineated according to
the procedures described in the MDH guidance for WHPA delineations in fractured and solution weathered bedrock (MDH, 2005). A composite WHPA was defined by combining the capture zones
delineated using these two methods.
3.1
Porous Media Flow Evaluation
The groundwater flow model discussed above was used to simulate the groundwater flow field in the
vicinity of North Branch. The WHPA for each of the NBWL wells was delineated using the software
program MODPATH (Pollock, 1994) with the modeled groundwater flow field. A minimum of 300
particles were distributed vertically surrounding the open interval of each well. These particles were
tracked backwards in time for both 1 and 10 years. When viewed in plan view, the areas
encompassed by the particle traces were then outlined as the one- and ten-year porous medium time
of travel zones for each well (Figure 5).
Porosity values used for the porous media evaluation were as follows: Quaternary sediments = 0.2,
Wonewoc Sandstone and Tunnel City Group = 0.253, Eau Claire Formation = 0.1, Mt. SimonHinckley Sandstone = 0.233, Proterozic Sediments = 0.1 Proterozoic basalt = 0.01 (Norvitch et al.,
1974, Schwartz and Zhang, 2003)
3.1.1 Sensitivity Analysis
A sensitivity analysis was performed for the model using the auto sensitivity option in Ground water
Vistas. The model was most sensitive to the horizontal hydraulic conductivity (K x) of the Quaternary
sediments (Zone 1 and Zone 8), and the horizontal and vertical hydraulic conductivities of the Tunnel
City Group/Wonewoc Sandstone (Zone 3). Output from the sensitivity analysis is presented in
Appendix E.
Multiple particle tracking simulations were conducted to account for uncertainty in the groundwater
flow model. For these simulations, the hydraulic conductivity values for the most sensitive hydraulic
conductivity zones (1, 3, and 8) were adjusted. The calibrated horizontal hydraulic conductivities of
Zone 1 and Zone 8 (Quaternary sediments) are 24 m/day and 22 m/day, respectively. The hydraulic
conductivities of these zones were adjusted to 1 m/day and 50 m/day based on the expected range in
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values for glacial sediments in the area. The calibrated horizontal and vertical hydraulic
conductivities of zone 3 (Tunnel City Group/Wonewoc Sandstone) are 12.8 m/day and 0.02 m/day,
respectively. The horizontal and vertical hydraulic conductivities of Zone 5 were adjusted plus and
minus 50%. Particle traces from all simulations were combined to define a composite porous media
flow capture zone as shown on Figure 5.
3.2
Fracture Flow Evaluation
The bedrock in the North Branch area is extensively faulted. Between NBWL Well 5 and Well 4 is
the Douglas Fault zone. Across the Douglas Fault zone up to 200 feet of vertical displacement has
occurred (Runkel and Boerboom, 2010). East of NBWL Well 6 is another unnamed fault where up to
100 feet of vertical displacement has occurred (Runkel and Boerboom, 2010). Between these
mapped fault features it is likely that additional smaller faults or fault zones may be present but are
difficult to define based on limited boring data. Because of the extensive faulting in the area,
fracture flow capture zones were delineated for all wells. Delineation technique 1 from MDH (2005)
was used for NBWL Wells 1 and 2. Delineation technique 2 (MDH, 2005) was used for NBWL
Wells 3, 5, and 6. Well 4 is open to a Quaternary sand and gravel aquifer. However, as shown on
Figure 2 this buried Quaternary aquifer is likely connected to the bedrock aquifer and may receive a
significant amount of water from the Mt. Simon Sandstone which is subsequently faulted in the
Douglas Fault zone. Also, the porous media flow evaluation indicated that particle traces originating
from Well 4 extend into the Mt. Simon Sandstone along the fault zone. Because of this connection,
delineation technique 4 (MDH, 2005) was used.
The fixed-radius fracture-flow capture zones defined for Well 3, Well 4, Well 5 and Well 6 were
extended upgradient based on gradients from the groundwater flow model (Figure 5). A five year
groundwater time of travel was used for the fixed radius capture zone and an additional five year
time of travel was used for the upgradient extensions per direction from MDH (MDH, 2011b). Fixed
radius capture zones were also extended along the orientation of faults in the area one mile from the
well unless a geologic boundary such as a mapped fault was encountered in which case the extension
was terminated at the geologic boundary. A summary of calculations used in the delineation of
fracture flow capture zones is presented in Appendix D.
3.3
Other Groundwater Withdrawal
Potential interference from other high capacity wells in the area was incorporated by including wells
from Minnesota DNR SWUDS database in the groundwater flow model. The base model (Barr,
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2005) used average pumping rates for 2004 for these other high capacity wells. For wells within two
miles of North Branch well pumping rates were updated to use the average from 2006 -2010. For the
fracture flow analysis, potential capture zones from other high capacity wells would not intersect the
capture zones for the NBWL wells so they were not included in the delineation of fracture flow
capture zones. Pumping from wells other than the NBWL wells was not adjusted to address future
use.
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4.0 Delineation of the Drinking Water Supply
Management Areas
The NBWL DWSMA encompasses the WHPA with boundaries that correspond to geographically
identifiable features (e.g., parcel boundaries, quarter section lines). Parcel boundaries where used as
much as possible in the delineation of the DWSMA. Quarter section lines where used in limited areas
where large parcels are intersected by quarter section lines. The DWSMA extends into North Branch
Township and Isanti County to the west. The DWSMA that encompasses the 10-year groundwater time
of travel zones is shown on Figure 6.
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5.0 Well Vulnerability Assessment
MDH evaluated the vulnerability of NBWL municipal wells to contamination from contaminants released
at the surface. The evaluation parameters include geology, well construction, pumping rate, and water
quality. All NBWL wells are classified as being not vulnerable. Copies of the MDH well vulnerability
scoring sheet for the NBWL wells are presented in Appendix C.
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6.0 Drinking Water Supply Management Area
Vulnerability Assessment
The vulnerability of the bedrock aquifers supplying NBWL Wells 1, 2, 3, 5, and 6 and the buried
Quaternary sand and gravel aquifer supplying NBWL Well 4 were assessed. The vulnerability of the
DWSMA associated with the NBWL wells was evaluated using geologic logs for wells located within and
surrounding the DWSMA along with previous mapped data from the Minnesota Geological Survey.
Geologic logs listed in the Minnesota Geological Survey (MGS) County Well Index for wells in the
vicinity of the DWSMA were reviewed and “L scores” based on the thickness of low permeability units at
each well location were assigned to each well. (See MnDNR (1991) for a discussion of how to determine
L scores). Aquifer vulnerability was further assessed using the geologic cross sections, bedrock geology
map (Runkel and Boerboom, 2010 ), surficial geology (Meyer, 2010a), and the Quaternary stratigraphy
model of Meyer (2010b). These data were used to construct three cross sections (Figure 2 through
Figure 4). Locations of these cross sections are shown on Figure 1. The low levels of tritium (below the
detection limit of 0.8 tritium units) in Well 3, Well 4, and Well 5 were also considered in assessing
aquifer vulnerability.
The entire DWSMA is assigned a vulnerability rating of “low” indicating that water moving vertically
from the surface will have several decades to a century to reach the aquifer(s). All NBWL wells have a
geologic sensitivity rating of low to very-low due to thick confining units of glacial clay (Appendix E).
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7.0 Supporting Data Files
The groundwater model can be reviewed using MODFLOW (Harbaugh and McDonald, 1996).
MODPATH pathline files can be reviewed using MODPATH Version 3 ( Pollock, 1994)
All coordinates in the modeling files are based on UTM NAD 83 Zone 15 N datum. Elevations are in
meters above mean sea level (m MSL). Time units are days. Length units are meters.
GIS files are included in Appendix G. Descriptions are self-explanatory and some additional information
is available in the associated metadata. Shapefiles files are in UTM NAD 83 Zone 15 N datum.
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8.0 References
Barr Engineering Company (Barr), 2005. Groundwater Modeling Evaluation of Future Wells for the
North Branch Water and Light Commission. Prepared for WSB and Associated, Inc. November
2005.
Boerboom, T.J. 2010. Precambrian Bedrock Geology. , plate 5 in Geologic Atlas of Chisago County,
Minnesota, County Atlas Series Atlas C-22, Part A, University of Minnesota, St Paul.
Bonin, B.J. 2011. Email from B.J. Bonin of WSB and Associates, Inc. to John Greer of Barr
Engineering regarding projected use for North Branch Water and Light Well 6, received
December 2, 2011.
Bradbury, K.B., and E.R. Rothschild. 1985. A computerized technique for estimating the hydraulic
conductivity of aquifer from specific capacity data. Ground Water v. 23, no. 2, pp. 240-246.
Environmental Simulations, Inc., 2011. Guide to using Groundwater Vistas, Version 6,
Environmental Simulations Inc.
Harbaugh, A.W., and McDonald, M.G. 1996. User’s documentation for MODFLOW-96, an update to
the U.S. Geological Survey Modular Finite Difference Ground-Water Flow Model: U.S.
Geological Survey Open-File Report 96-485. 56p.
McDonald, M.G., and A.W. Harbaugh. 1988. A Modular Three-Dimensional Finite-Difference
Groundwater Flow Model, U.S. Geological Survey Techniques of Water Resource Investigations,
TWRI 6-A1. 575 p.
Meyer, G.N., 2010a. Surficial Geology. , plate 3 in Geologic Atlas of Chisago County, Minnesota,
County Atlas Series Atlas C-22, Part A, University of Minnesota, St Paul.
Meyer, G.N., 2010b. Quaternary Stratigraphy. , plate 4 in Geologic Atlas of Chisago County,
Minnesota, County Atlas Series Atlas C-22, Part A, University of Minnesota, St Paul.
Minnesota Department of Health (MDH). 2011a. Personal communication: Pre-delineation Meeting,
held on June 16, 2011 at Barr Engineering Company, Minneapolis MN.
Minnesota Department of Health (MDH). 2011b. Email summarizing time of travel for fracture flow
analysis. From Amal Djerrari of MDH to John Greer of Barr Engineering Company. Dated
August 19th, 2011.
Minnesota Department of Health (MDH). 2005. Draft Guidance for Delineating Wellhead Protection
Areas in Fractured and Solution-Weathered Bedrock in Minnesota. 81pp.
Minnesota Department of Natural Resources (MnDNR), Division of Waters. 1991. Criteria and
Guidelines for Assessing Geologic Sensitivity of Ground Water Resources in Minnesota. Prepared
for the Legislative Commission on Minnesota Resources. 122pp.
Mossler, J.H. and R.G. Tipping. 2000. Bedrock geology and structure of the seven-county Twin
Cities metropolitan area, Minnesota. Miscellaneous Map Series M-104, Minnesota Geological
Survey.
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Norvitch, R.F., Ross T.G., and Brietkrietz, A., 1974. Water resources outlook for the Minneapolis -St.
Paul metropolitan area. Metropolitan Council of the Twin Cities area, 219p.
Pollock, D.W. 1994. User’s guide for MODPATH/MODPATH-PLOT, Version 3: a particle tracking
post-processing package for MODFLOW, the U.S. Geological Survey finite difference ground water flow model. U.S. Geological Survey Open-File Report 94-464.
Runkel, A.C.and Boerboom, T.J. 2010. Bedrock Geology, plate 2 in Geologic Atlas of Chisago
County, Minnesota, County Atlas Series Atlas C-22, Part A, University of Minnesota, St Paul.
Schwartz, F.W. and Zhang, H., 2003. Fundamentals of Ground Water. John Wiley and Sons, Inc.
New York, New York.
Tipping, R.G., Runkel, A.C., and Gonzalez, C.M. 2010. Geologic Investigation for Portions of the
Twin Cities Metropolitan Area: I Quaternary/Bedrock Hydraulic Conductivity, II/ Groundwater
Chemistry. Metropolitan Council Water Supply master Plan Development, November 24, 2010
P:\Mpls\23 MN\13\23131005 No Branch Pt 1 WPP\WorkFiles\Report\North Branch Part 1 WHPP.docx
16
Tables
Table 1
Assessment of Data Elements
Delineation
Criteria
Quality and
Quantity of
Well Water
Land and
Groundwater
Use in
DWSMA
Data Element
Use of the
Well s
Present and Future
Implications
M
M
M
L
H
H
H
L
H
H
H
L
H
H
H
L
MGS, CWI
MGS, MDH, CWI
MGS
Not Available
L
L
L
H
L
H
L
L
L
L
L
L
WSB and Associates
MNGEO
DNR
L
M
L
L
MNDOT
H
H
H
H
North Branch Water and Light, CWI, MDH
files
Data Source
Precipitation
Geology
Maps and geologic descriptions
Subsurface data
Borehole geophysics
Surface geophysics
Maps and soil descriptions
Eroding lands
Water Resources
Watershed units
List of public waters
Shoreland classifications
Wetlands map
Floodplain map
Land Use
Parcel boundaries map
Political boundaries map
PLS map
Land use map and inventory
Comprehensive land use map
Zoning map
Public Utility Services
Transportation routes and
corridors
Storm/sanitary sewers and PWS
system map
Oil and gas pipelines map
Public drainage systems map/list
Records of well construction,
maintenance, and use
Definitions Used for Assessing Data Elements:
High (H) the data element has a direct impact
Moderate (M) the data element has an indirect or marginal impact
Low (L) the data element has little if any impact
Shaded the data element was not required by MDH for preparing the WHP plan
CWI – Minnesota County Well Index
DNR – Minnesota Department of Natural Resource
MNGEO - Minnesota Geospatial Information Office
MDH – Minnesota Department of Health
MNDOT – Minnesota Department of Transportation
MPCA – Minnesota Pollution Control Agency
NRCS – Natural Resources Conservation Service
SSURGO – Soil Survey Geographic Database
USGS – United State Geological Survey
Table 1
Assessment of Data Elements (Continued)
Delineation
Criteria
Quality and
Quantity of
Well Water
Land and
Groundwater
Use in
DWSMA
Data Element
Use of the
Well s
Present and Future
Implications
M
M
L
M
DNR
H
L
H
H
L
H
H
L
H
H
L
H
DNR
DNR
CWI, MDH
H
H
H
M
H
H
H
M
H
H
H
M
H
H
H
M
MDH
MDH
Not Available
MPCA, MDH
M
M
M
M
MDH, MPCA
Data Source
Surface Water Quantity
Stream flow data
Ordinary high water mark data
Permitted withdrawals
Protected levels/flows
Water use conflicts
Groundwater Quantity
Permitted withdrawals
Groundwater use conflicts
Water levels
Surface Water Quality
Stream and lake water quality
management classification
Monitoring data summary
Groundwater Quality
Monitoring data
Isotopic data
Tracer studies
Contamination site data
Property audit data from
contamination sites
MPCA and MDA spills/release
reports
Definitions Used for Assessing Data Elements:
High (H) the data element has a direct impact
Moderate (M) the data element has an indirect or marginal impact
Low (L) the data element has little if any impact
Shaded the data element was not required by MDH for preparing the WHP plan
CWI – Minnesota County Well Index
DNR – Minnesota Department of Natural Resource
MNGEO - Minnesota Geospatial Information Office
MDH – Minnesota Department of Health
MNDOT – Minnesota Department of Transportation
MPCA – Minnesota Pollution Control Agency
NRCS – Natural Resources Conservation Service
SSURGO – Soil Survey Geographic Database
USGS – United State Geological Survey
2
Table 2
Annual and Projected Pumping Rates for North Branch Wells
Total Annual Withdrawal (gal/yr)
Unique
Number Well Name
1
217922
2
112244
3
522767
4
706844
5
749383
6
593584
Totals
2006
159,891,000
36,396,000
5,872,000
28,112,000
0
0
230,271,000
2007
158,063,000
50,106,000
3,352,000
27,832,000
0
0
239,353,000
2008
91,027,000
12,814,000
65,103,000
43,557,000
0
0
212,501,000
2009
3,942,000
350,000
129,316,000
81,604,000
13,254,000
0
228,466,000
2010
209,000
0
124,964,000
74,783,000
806,000
15,390
200,777,390
Source: MN DNR SWUDS Database
Percentage of Annual Withdrawal
Unique
Number Well Name
1
217922
2
112244
3
522767
4
706844
5
749383
6
593584
2006
69.4%
15.8%
2.6%
12.2%
0.0%
0.0%
2007
66.0%
20.9%
1.4%
11.6%
0.0%
0.0%
2008
42.8%
6.0%
30.6%
20.5%
0.0%
0.0%
Projected Water Use (2015)
Unique
Number Well Name
217922
1
112244
2
522767
3
706844
4
749383
5
593584
6
Totals
Total1 (gal/yr)
292,700,000
% of Total
Projected
Water Use
Well1
36.0%
8.6%
30.7%
23.5%
1.2%
0.0%
Projected Well
Pumpage
Based on %
(gal/yr)
105,372,000
25,172,200
89,858,900
68,784,500
3,512,400
0
292,700,000
2009
1.7%
0.2%
56.6%
35.7%
5.8%
0.0%
2010
0.1%
0.0%
62.2%
37.2%
0.4%
0.0%
Average Annual
% of
Withdrawal
36.0%
8.6%
30.7%
23.5%
1.2%
0.0%
Maximum Total Pumping for Model Input2
gal/yr
159,891,000
50,106,000
129,316,000
81,604,000
13,254,000
21,000,000
455,171,000
gal/day
438,058
137,277
354,290
223,573
36,312
57,534
1,247,044
1
Percentages for Wells 1 through 6 are based the average annual % of annual withdrawal for the period 2005 thorugh 20009.
2
Well 6 rate of 21 mg/yr represents sum of estimated pumping for irrigation (17 mg/yr) and municipal peak demand (4 mg/yr) that
was provided by WSB & Associates
Page 1 of 1
Mpls\23 MN\13\23131005 No Branch Pt 1 WPP\WorkFiles\Well Pumping & Water Use Projection.xls
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Barr Footer: ArcGIS 10.0, 2012-08-07 10:10 File: I:\Projects\23\13\1005\Maps\Reports\Bedrock_Geology_Cross_Sections2.mxd User: JCG
>
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BEDROCK!> !>!>GEOLOGY
WHPP!>Part 1
North
Branch Municipal
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> Water and Light
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Chisago County, MN
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Douglas Fault shown as a single fault offset for simplicity.
Data are not sufficient to know if the offset is from a single
fault or a series of faults with less displacement
Figure 2
GEOLOGIC CROSS SECTION A-A'
WHPP Part 1
North Branch Municipal
Water and Light
Chisago County, MN
Douglas Fault shown as a single fault offset for simplicity.
Data are not sufficient to know if the offset is from a single
fault or a series of faults with less displacement
Figure 3
GEOLOGIC CROSS SECTION B-B'
WHPP Part 1
North Branch Municipal
Water and Light
Chisago County, MN
Figure 4
GEOLOGIC CROSS SECTION C-C'
WHPP Part 1
North Branch Municipal
Water and Light
Chisago County, MN
30
North Branch
North Branch Township
7
6
5
4
95
<
&
North Branch Water & Light Well
Composite 10 Year Porous Media Capture Zone
1 Year Porous Media Capture Zone
1 Year Fracture Flow Capture Zone
Well 1
Well 3
13
Well 4
Muncipal Boundary
Water Body
95
<
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<
Well 6
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Kilometers
0.5
1
1
Chisago Co.
Figure 5
Isanti Co.
Barr Footer: ArcGIS 10.0, 2012-07-26 13:11 File: I:\Projects\23\13\1005\Maps\Reports\Well_Capture_Zones_rvised_7-2-2012.mxd User: JCG
Well 5
7
6
5
4
Well 2
10 Year Fracture Flow Capture Zone
§
¨
¦
35
WELL CAPTURE ZONES
WHPP Part 1
North Branch Municipal
Water and Light
Chisago County, MN
North Branch
North Branch Township
30
7
6
5
4
North Branch Water & Light Well
<
&
DWSMA
Composite 10 Year WHPA
Muncipal Boundary
Water Body
95
Well 5
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Well 3
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Well 2
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Well 6
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0
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1
1
Chisago Co.
Figure 6
Isanti Co.
Barr Footer: ArcGIS 10.0, 2012-08-08 08:57 File: I:\Projects\23\13\1005\Maps\Reports\WHPA_DWSMA_revised_7-26-2012.mxd User: JCG
Well 1
§
¦
¨
35
WHPA & DWSMA
WHPP Part 1
North Branch Municipal
Water and Light
Chisago County, MN
Appendices
Appendix A
Well Construction Records
Appendix B
Aquifer Test Data and Analysis
Environmental Health Division
Drinking Water Protection Section
Source Water Protection Unit
P.O. Box 64975
St. Paul, Minnesota 55164-0975
Aquifer Test Plan
Public Water Supply ID: 130011
PWS Name: North Branch Water and Light
Contact
Aquifer Test Contact: John Greer
Contractor Name and Address: Barr Engineering
4700 West 77th Street
City, State, Zip: Minneapolis, MN 55435-4803
Phone and Fax Number: 952-832-2691 (phone) 952-832-2601 (fax)
Proposed Aquifer Test Method
1)
An existing pumping test that meets the requirements of wellhead protection rule part 4720.5520
and that was previously conducted on a public well in your water supply system.
2) An existing pumping test that meets the requirements of wellhead protection rule part 4720.5520
and that was previously conducted on another well in a hydrogeologic setting determined by the
department to be equivalent.
3)
A pumping test conducted on a new or existing public well in your water supply system and that
meets the requirements for larger sized water systems (wellhead protection rule part 4720.5520).
4)
A pumping test conducted on a new or existing public well in your water supply system and that
meets the requirements for smaller sized water systems (wellhead protection rule part 4720.5530).
5) An existing pumping test that does not meet the requirements of wellhead protection rule
part 4720.5520 and that was previously conducted on: 1) a public water supply well or 2) another well
in a hydrogeologic setting determined by the department to be equivalent.
X
6)
An existing specific capacity test or specific capacity test for the public water supply well.
7)
An existing published transmissivity value.
Include all pumping test data and the estimated transmissivity value when the aquifer test method proposed
is one of those specified in Nos. 1, 2, 5, 6, or 7 listed above.
To request this document in another format, please call the Section Receptionist at (651) 201-4700 or Division TTY at (651) 201-5797.
HE-01555-01 (10/06)
IC #140-0606
Test Description
Pumped Well
706844 (North Branch #4)
Unique No:
Location
(Township, Range, T35 R21W Sec19 DBCBAC
Section, Quarters):
Number of
0
Observation Wells:
X
Confined
Test Duration
24
(Hours):
Pump Type:
Discharge Rate: 325 gpm
Flow Rate Measuring
Device Type:
Unconfined
You must include a map showing the location of the pumping well and observation well(s).
Rational for Proposed Test Method
Briefly describe the rationale for method selected:
Specific capacity data for buried quaternary aquifer. Only known test data for the unit the well is open
to.
Using the TGuess Method (Bradbury and Rothschild, 1985) the transmissivity of the aquifer is estimated
to be 1728 ft2/day, and a hydraulic conductivity of 29 ft/day.
Regional data from the MGS/MCES hydraulic conductivity database for buried Quaternary aquifers in
the area has the following characteristics (n= 89):
Minimum K = 4.6 ft/day
Maximum K = 221.4 ft/day
Geometric Mean K = 20.3 ft/day
List all unique numbers of wells that this Aquifer Test Plan applies to:
706844 (Well 4)
Reviewed by:
Approved:
Yes
No
Approval Date:
Worksheet for Estimating Transmissivity and Hydraulic Conductivity from Specific Capacity Test Data
Maximum iterations
Error tolerance (as drawdown)
Explanation and notes attached.
Field Data
Estimated Parameters
Depth to Water
Location
Well
Diam.
Initial
Final
North Branch Well 4
inches
18
feet
33.0
feet
78.0
Calculated Results
Screened Interval
Mean
Test
Pumping
Duration
Rate
hours
24
gpm
325.0
Depth to
Top
Depth to
Bottom
Storage
Coeff.
(S)
Well loss
Coeff.
(C)
Aquifer
Thickness
(b)
feet
158.0
feet
218.0
0.001
sec^2/ft^5
feet
60
0
Measured
Drawdown
(sm)
feet
45.00
Saturated
Screen
Length
(L)
feet
60.0
100
0.001 feet
Diagnostics
Well loss
(sw)
feet
0.0E+00
Partial
Penetration
Parameter
(sp)
0.00
Solution Integrity
Well Bore
Error as
Storage
Drawdown
Test
Specific
Capacity
Transmissivity
(T)
Conductivity
(K)
Calculated
Drawdown
gpm/ft
7.22
sq ft/sec
2.0E-02
ft/day
2.9E+01
feet
45.00
References:
Bradbury, K.B., and E.R. Rothschild, 1985. A computerized technique for estimating the hydraulic conductivity of aquifer from specific capacity data: Ground Water vol. 23, No. 2, pp. 240-246.
ASTM International, 2004. Standard Test Method for Determining Specific Capacity and Estimating Transmissivity at the Control Well, Standard D 5472-93, in Annual Book of ASTM Standards, Vol. 04.08 pp. 1279-1282.
0.00%
pass
Sensitivity of T:
to S at
± 1 factor of
to sw at
to b at
10
± 25%
10% of sm
sq ft/sec
sq ft/sec
sq ft/sec
3.2E-03
2.4E-03
3.0E-03
Worksheet for Estimating Transmissivity and Hydraulic Conductivity from Specific Capacity Test Data
Explanation
This spreadsheet estimates transmissivity and hydraulic conductivity following the method of Bradbury and Rothschild (1985). The method applies the CooperJacob approximation of the Theis equation, with corrections for partial penetration and well loss, as indicated in equations 1-4.
  2 .25 Tt
 ln 
4π ( s m − s w )   rw 2 S
Q


 + 2s p 



Eq. 1
T =
Equation 1 is the modified Cooper-Jacob approximation of the Theis equation for transient radial flow to a well in a confined aquifer. Equation 2 calculates well
loss, based on a correction factor (C), which must be estimated or determined by alternate test methods. Equation 3 calculates a unitless partial penetration
correction factor (see assumptions below), employing the function G(L/b), approximated in Equation 4 with a polynomial best-fit.
Eq. 2
s w = CQ 2
The estimates of transmissivity and conductivity yielded by this method are imperfect, and presumed to be less realistic than the estimates that can be made from
time/drawdown or distance/drawdown tests, if those data are available. This solution method includes several assumptions that should limit the confidence
placed in its estimates:
Eq. 3
sp =
Eq. 4
G( L / b) = 2.948 − 7.363( L / b) + 11.447( L / b)2 − 4.675( L / b)3
a)
b)
c)
d)
the tested aquifer is confined, non-leaky, homogeneous and isotropic;
the storage coefficient of the aquifer is known;
the well loss is known;
the effective aquifer thickness is known.

1− L / b  b
 ln − G( L / b) 
L / b  rw

In most cases, the storage coefficient, well loss, and aquifer thickness can only be estimated. The error introduced is non-negligible, but can be loosely
bracketed. The diagnostic section of the worksheet includes a limited sensitivity analysis.
If the user has little control on well loss, or aquifer thickness, the well loss and partial penetration correction terms may be removed, respectively, by setting the
well loss coefficient (C) equal to zero, and the aquifer thickness (b) equal to the saturated screen interval. Note that the partial penetration correction factor
assumes isotropic conditions (Kh = Kz), and gives a value of T extrapolated from the screened interval to the full aquifer thickness. If the aquifer is anisotropic,
this correction is inappropriate.
b - aquifer thickness
sm - measured drawdown
C - well loss coefficient
sw - well loss
L - screen length
sp - partial penetration parameter
Q - mean pumping rate
rw - effective radius
S - storativity
T - transmissivity
t - pumping duration
Usage Notes
Units
The user may chose any combination of units for field data, estimated parameters and calculated results by
changing the units shown in the column headers. Each of these cells has an embedded pull down list from which to
chose. Only the listed options will work, because the embedded functions look for specific text strings. The units of
the diagnostic columns are linked to the calculated results, and shouldn't be manually changed.
Input
Field data may be pasted in or entered directly. The units header should be changed to agree with the data. All
depth values are assumed to be from a common reference point (e.g., ground surface).
Calculated Results
The calculated results cells all make use of user-defined functions written in Visual Basic for Applications. The
functions and their arguments are listed to the right. The code may be viewed by opening Excel's Visual Basic
Editor. Cells containing these functions may be drag-filled or copied down their respective columns to extend the
table. Changing the units in the column header will automatically change the output units.
Diagnostics
The difference between calculated drawdown the measured drawdown is a metric for assessing the convergence of
the solution. If the error is unacceptably high, the maximum iterations and error tolerance may be adjusted in the
fields above the table. The well bore storage test checks that the specific capacity test rate and duration were
adequate to negate the influence of water removed from the well casing on the measured drawdown. The test
applies criterion that the test duration be longer than 25*rw2/T (ASTM, 2004). Note that this check assumes well
radius and riser radius are equal.
The worksheet assesses the sensitivity of transmissivity to variation in the storage coefficient (S), to the degree of
well loss (sw), and to the effective isotropic aquifer thickness (b). The resulting values shown indicate the variance
of T from the actual estimate, when the target parameter is adjusted as indicated.
Functions and arguments employed in this workbook
CalcDD(TGuess(well diam., diam. units, t, t units, Q, Q units, S, sw, sw units, sp, T, T units, output units)
Returns drawdown calculated from an estimated T.
Getdd(dtw initial, dtw initial units, dtw final, dtw final units, output units)
Returns drawdown calculated from measured depth to water (dtw)
GetK(T, T units, b, b units, output units)
Returns an estimate of hydraulic conductivity calculated by T/b.
Getloss(Q, Q units, C, C units, output units)
Returns the well loss correction factor (s w ).
Getsl(screen top depth, screen top depth units, screen bottom depth, screen bottom depth units, dtw init., dtw units, output units)
Returns the saturated screen length computed from field data.
GetSpCap(Q, Q units, sm, sm units, output units)
Returns specific capacity.
ppen(L, L units, b, b units, d, d units)
Returns the partial penetration correction factor (s p ).
TGuess(well diam., diam. units, sm, sm units, t, t units, Q, Q units, S, sw, sw units, sp, error tolerance, error units, max. steps, output units)
Return an estimate of transmissivity.
wellstorage(well diam., diam. units, t, t units, T, T units)
Returns the text "pass" or "fail" based on a test for inappropriate effects of well bore storage.
References
1) Bradbury, K.B., and E.R. Rothschild, 1985. A computerized technique for estimating the hydraulic conductivity of aquifer from
specific capacity data: Ground Water vol. 23, No. 2, pp. 240-246.
2) ASTM International, 2004. Standard Test Method for Determining Specific Capacity and Estimating Transmissivity at the Control
Well, Standard D 5472-93, in Annual Book of ASTM Standards, Vol. 04.08 pp. 1279-1282.
Questions/Bugs, contact:
Michael Cobb, UW-Madison Department of Geology and Geophysics, [email protected]
Regional Hydraulic Conductivity Data
Burried Quaternary Aquifer, North Branch, MN area
Unique
Number
196274
635118
592602
582658
558466
401041
723636
634730
609614
648862
631243
676809
637970
598048
653760
687641
577029
743250
523887
548322
694483
431738
656439
676819
550632
620344
676821
562762
598047
452262
436594
575644
544275
588782
641068
631543
582657
638933
750853
562384
631244
648809
448288
701584
648874
562374
706844
641069
635113
712512
653108
620424
T
T units
450
685
715
581
3011
418
1631
592
3330
528
427
715
3878
2872
578
230
901
133
6951
728
692
1530
424
332
248
454
164
1684
2872
236
976
604
1042
3330
581
728
604
319
505
1235
703
824
597
257
460
607
1441
581
268
308
184
8854
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
T analytical
method
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
Aquifer
Thickness
(ft)
40
25
40
47
38
40
33
40
40
34
20
40
40
40
31
40
40
11
47
40
89
40
21
40
31
43
27
34
40
18
40
40
40
40
47
40
49
29
22
40
26
40
30
40
39
40
92
47
20
21
40
40
Kh
(ft/day)
11.25
27.39
17.88
12.37
79.23
10.44
49.42
14.79
83.24
15.52
21.36
17.88
96.94
71.8
18.66
5.76
22.52
12.08
147.89
18.21
7.78
38.26
20.2
8.31
8
10.55
6.08
49.54
71.8
13.1
24.4
15.09
26.05
83.24
12.37
18.21
12.32
11.01
22.94
30.87
27.05
20.61
19.89
6.42
11.79
15.17
15.66
12.37
13.39
14.66
4.6
221.35
Test Method
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Aquifer
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
UTM E
UTM N
498226
498518
498632
499032
498795
497516
498304
498850
498645
498876
498574
498829
498460
498399
498585
499181
500157
498338
499146
498736
499159
500121
498584
499380
499336
498847
498864
498821
498626
498670
499623
498820
498817
499821
498988
498548
499019
498875
499448
498863
498630
498604
498572
499775
499063
498866
499154
498900
498406
499837
499936
498424
5039058
5040055
5037652
5038335
5037705
5038455
5039972
5037506
5038303
5037440
5037343
5037436
5040333
5038966
5037967
5040301
5040507
5038233
5038080
5040221
5038980
5040479
5037357
5038067
5038384
5037664
5037341
5037974
5038756
5040485
5040485
5037774
5039546
5039549
5037560
5037580
5038150
5037285
5038066
5037929
5037387
5037295
5037908
5037594
5037503
5037859
5038991
5037512
5040330
5037259
5040510
5038694
Regional Hydraulic Conductivity Data
Burried Quaternary Aquifer, North Branch, MN area
Unique
Number
537809
650479
630000
714530
550817
656440
648810
637166
537762
680158
670616
626935
676482
714544
642633
164698
636073
720477
656441
542625
626578
676820
542591
690008
631224
565325
577039
644684
720543
653791
569998
657009
676808
550631
136128
582662
614429
Min
Max
Average
Geomean
T
T units
401
1173
1544
3115
304
852
606
390
285
373
367
870
246
7217
667
9941
1055
592
457
760
1434
901
568
528
791
1179
548
592
290
390
607
1231
901
279
1417
604
1212
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
ft^2/day
T analytical
method
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
TGUESS
Aquifer
Thickness
(ft)
40
40
40
24
34
34
29
40
20
38
34
28
40
49
46
79
40
40
29
40
48
40
40
35
40
22
29
40
40
40
32
40
40
37
40
49
40
Kh
(ft/day)
10.03
29.32
38.59
129.79
8.95
25.05
20.9
9.74
14.23
9.81
10.8
31.07
6.14
147.28
14.51
125.84
26.38
14.81
15.77
19.01
29.88
22.52
14.19
15.1
19.77
53.61
18.9
14.79
7.24
9.74
18.96
30.77
22.52
7.55
35.43
12.32
30.31
4.6
221.4
30.3
20.3
Test Method
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Specific Capacity
Aquifer
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
QBAA
UTM E
UTM N
499392
498330
498422
500023
498675
498723
498882
499860
498272
499015
498975
498627
498519
498999
498934
499867
499382
498359
498664
498670
499001
498788
498599
498371
498661
498713
499980
498674
498281
498751
498812
499269
498636
499277
498116
499024
498622
5038339
5038679
5038389
5038309
5037727
5037402
5037386
5037553
5039494
5037490
5037460
5040099
5038328
5038008
5038396
5037535
5039347
5040097
5037347
5037893
5038275
5037320
5037650
5040008
5037437
5037906
5037164
5037578
5039497
5037495
5037909
5038261
5037528
5038345
5038075
5038074
5038768
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N
0
North Branch Wells
>
!
Feet
1,000
Quaternary Wells with Specific Capacity Data
2,000
Quaternary Wells with Specific Capactiy Data
North Branch Water and Light
Environmental Health Division
Drinking Water Protection Section
Source Water Protection Unit
P.O. Box 64975
St. Paul, Minnesota 55164-0975
Aquifer Test Plan
Public Water Supply ID: 130011
PWS Name: North Branch Water and Light
Contact
Aquifer Test Contact: John Greer
Contractor Name and Address: Barr Engineering
4700 West 77th Street
City, State, Zip: Minneapolis, MN 55435-4803
Phone and Fax Number: 952-832-2691 (phone) 952-832-2601 (fax)
Proposed Aquifer Test Method
X
1)
An existing pumping test that meets the requirements of wellhead protection rule part 4720.5520
and that was previously conducted on a public well in your water supply system.
2) An existing pumping test that meets the requirements of wellhead protection rule part 4720.5520
and that was previously conducted on another well in a hydrogeologic setting determined by the
department to be equivalent.
3)
A pumping test conducted on a new or existing public well in your water supply system and that
meets the requirements for larger sized water systems (wellhead protection rule part 4720.5520).
4)
A pumping test conducted on a new or existing public well in your water supply system and that
meets the requirements for smaller sized water systems (wellhead protection rule part 4720.5530).
5) An existing pumping test that does not meet the requirements of wellhead protection rule
part 4720.5520 and that was previously conducted on: 1) a public water supply well or 2) another well
in a hydrogeologic setting determined by the department to be equivalent.
6)
An existing specific capacity test or specific capacity test for the public water supply well.
7)
An existing published transmissivity value.
 Include all pumping test data and the estimated transmissivity value when the aquifer test method proposed
is one of those specified in Nos. 1, 2, 5, 6, or 7 listed above.
To request this document in another format, please call the Section Receptionist at (651) 201-4700 or Division TTY at (651) 201-5797.
HE-01555-01 (10/06)
IC #140-0606
Test Description
Pumped Well
749383 (North Branch #5)
Unique No:
Location
(Township, Range, T35 R21W Sec19 CBBADA
Section, Quarters):
Number of
1 (TW10, 706835)
Observation Wells:
X
Confined
Test Duration
192 (Multiple-steps)
(Hours):
Pump Type:
Discharge Rate: Variable (0-2000 gpm)
Flow Rate Measuring
Bernoulli Tube
Device Type:
Unconfined
 You must include a map showing the location of the pumping well and observation well(s).
Rational for Proposed Test Method
Briefly describe the rationale for method selected:
This pumping test has multiple steps with multiple recovery periods. The last step was 24 hours in length.
Data was analyzed by MDH staff. This is the most complete and longest test available for the Mt SimonHinckley aquifer in the area. The monitoring well was also open to the Tunnel City – Wonewoc aquifer
and allows for estimation of the leakage through the Eau Claire Formation.
Transmissivity as determined by MDH is 5370 ft2/day
Using a aquifer thickness of 150 feet results in a hydraulic conductivity of 35.8 ft/day
List all unique numbers of wells that this Aquifer Test Plan applies to:
522767 (Well 3)
749383 (Well 5)
Reviewed by:
Approved:
Yes
No
Approval Date:
>
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00153497
>
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Well 5
00749383
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TW-10
00706835
00500210
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>
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00196274
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00598033
>
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00598048
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00614454
>
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00608039
>
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>
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;
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N
>
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Feet
0
100
>
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>
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>
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100
Well 5 Pumping Test
North Branch Water and Light
>
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>
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>
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100.
Displacement (ft)
10.
1.
0.1
0.01
1.
10.
100.
1000.
1.0E+4
1.0E+5
Time (min)
WELL TEST ANALYSIS
Data Set: P:\...\North Branch Well 5 pumptest_test Aug - Sept 2007_MDH.aqt
Date: 11/17/11
Time: 12:33:04
PROJECT INFORMATION
Company: MDH
Location: North Branch
Test Well: Test Well 10
Test Date: Feb 10, 2006
AQUIFER DATA
Saturated Thickness: 146. ft
Aquitard Thickness (b'): 20. ft
Anisotropy Ratio (Kz/Kr): 1.
Aquitard Thickness (b"): 20. ft
WELL DATA
Well Name
Well 5
Pumping Wells
X (ft)
Y (ft)
Well Name
1635387.1416532627.95 Test Well 10
Well 5
Observation Wells
X (ft)
Y (ft)
1635416.6716532562.34
1635387.1416532627.95
SOLUTION
Aquifer Model: Leaky
T = 5371.2 ft2/day
1/B = 0.0002008 ft-1
T2 = 2034.1 ft2/day
Solution Method: Neuman-Witherspoon
S = 0.002951
ß/r = 1.455E-5 ft-1
S2 = 6.31E-5
Environmental Health Division
Drinking Water Protection Section
Source Water Protection Unit
P.O. Box 64975
St. Paul, Minnesota 55164-0975
Aquifer Test Plan
Public Water Supply ID: 130011
PWS Name: North Branch Water and Light
Contact
Aquifer Test Contact: John Greer
Contractor Name and Address: Barr Engineering
4700 West 77th Street
City, State, Zip: Minneapolis, MN 55435-4803
Phone and Fax Number: 952-832-2691 (phone) 952-832-2601 (fax)
Proposed Aquifer Test Method
1)
An existing pumping test that meets the requirements of wellhead protection rule part 4720.5520
and that was previously conducted on a public well in your water supply system.
2) An existing pumping test that meets the requirements of wellhead protection rule part 4720.5520
and that was previously conducted on another well in a hydrogeologic setting determined by the
department to be equivalent.
3)
A pumping test conducted on a new or existing public well in your water supply system and that
meets the requirements for larger sized water systems (wellhead protection rule part 4720.5520).
4)
A pumping test conducted on a new or existing public well in your water supply system and that
meets the requirements for smaller sized water systems (wellhead protection rule part 4720.5530).
5) An existing pumping test that does not meet the requirements of wellhead protection rule
part 4720.5520 and that was previously conducted on: 1) a public water supply well or 2) another well
in a hydrogeologic setting determined by the department to be equivalent.
X
6)
An existing specific capacity test or specific capacity test for the public water supply well.
7)
An existing published transmissivity value.
 Include all pumping test data and the estimated transmissivity value when the aquifer test method proposed
is one of those specified in Nos. 1, 2, 5, 6, or 7 listed above.
To request this document in another format, please call the Section Receptionist at (651) 201-4700 or Division TTY at (651) 201-5797.
HE-01555-01 (10/06)
IC #140-0606
Test Description
Pumped Well
112244 (North Branch #2)
Unique No:
Location
(Township, Range, T35 R21W Sec21 BBCDBA
Section, Quarters):
Number of
0
Observation Wells:
X
Confined
Test Duration
Unknown
(Hours):
Pump Type:
Discharge Rate: 350 gpm
Flow Rate Measuring
Device Type:
Unconfined
 You must include a map showing the location of the pumping well and observation well(s).
Rational for Proposed Test Method
Briefly describe the rationale for method selected:
Specific capacity data for the Fond du lac aquifer (Proterozoic sediments). The only other high capacity
well in the area open to this aquifer is North Branch Well 1 (217922) and as noted on the well log the
specific capacity for that well is incongruous.
Using the TGuess Method (Bradbury and Rothschild, 1985) the transmissivity of the aquifer is estimated
to be 441 ft2/day, and a hydraulic conductivity of 4.4 ft/day.
List all unique numbers of wells that this Aquifer Test Plan applies to:
217922 (Well 1)
112244 (Well 2)
Reviewed by:
Approved:
Yes
No
Approval Date:
Worksheet for Estimating Transmissivity and Hydraulic Conductivity from Specific Capacity Test Data
Maximum iterations
Error tolerance (as drawdown)
Explanation and notes attached.
Field Data
Estimated Parameters
Depth to Water
Location
Well
Diam.
Initial
Final
North Branch Well 2
inches
10
feet
32.0
feet
215.0
Calculated Results
Screened Interval
Mean
Test
Pumping
Duration
Rate
hours
12
gpm
350.0
Depth to
Top
Depth to
Bottom
Storage
Coeff.
(S)
Well loss
Coeff.
(C)
Aquifer
Thickness
(b)
feet
261.0
feet
360.0
0.001
sec^2/ft^5
feet
100
0
Measured
Drawdown
(sm)
feet
183.00
Saturated
Screen
Length
(L)
feet
99.0
100
0.001 feet
Diagnostics
Well loss
(sw)
feet
0.0E+00
Partial
Penetration
Parameter
(sp)
0.03
Solution Integrity
Well Bore
Error as
Storage
Drawdown
Test
Specific
Capacity
Transmissivity
(T)
Conductivity
(K)
Calculated
Drawdown
gpm/ft
1.91
sq ft/sec
5.1E-03
ft/day
4.4E+00
feet
183.00
Note: Test duration assumed to be 12 hours
References:
Bradbury, K.B., and E.R. Rothschild, 1985. A computerized technique for estimating the hydraulic conductivity of aquifer from specific capacity data: Ground Water vol. 23, No. 2, pp. 240-246.
ASTM International, 2004. Standard Test Method for Determining Specific Capacity and Estimating Transmissivity at the Control Well, Standard D 5472-93, in Annual Book of ASTM Standards, Vol. 04.08 pp. 1279-1282.
0.00%
pass
Sensitivity of T:
to S at
± 1 factor of
to sw at
to b at
10
± 25%
10% of sm
sq ft/sec
sq ft/sec
sq ft/sec
8.4E-04
6.0E-04
1.2E-03
Worksheet for Estimating Transmissivity and Hydraulic Conductivity from Specific Capacity Test Data
Explanation
This spreadsheet estimates transmissivity and hydraulic conductivity following the method of Bradbury and Rothschild (1985). The method applies the CooperJacob approximation of the Theis equation, with corrections for partial penetration and well loss, as indicated in equations 1-4.
  2 .25 Tt
 ln 
4π ( s m − s w )   rw 2 S
Q


 + 2s p 



Eq. 1
T =
Equation 1 is the modified Cooper-Jacob approximation of the Theis equation for transient radial flow to a well in a confined aquifer. Equation 2 calculates well
loss, based on a correction factor (C), which must be estimated or determined by alternate test methods. Equation 3 calculates a unitless partial penetration
correction factor (see assumptions below), employing the function G(L/b), approximated in Equation 4 with a polynomial best-fit.
Eq. 2
s w = CQ 2
The estimates of transmissivity and conductivity yielded by this method are imperfect, and presumed to be less realistic than the estimates that can be made from
time/drawdown or distance/drawdown tests, if those data are available. This solution method includes several assumptions that should limit the confidence
placed in its estimates:
Eq. 3
sp =
Eq. 4
G( L / b) = 2.948 − 7.363( L / b) + 11.447( L / b)2 − 4.675( L / b)3
a)
b)
c)
d)
the tested aquifer is confined, non-leaky, homogeneous and isotropic;
the storage coefficient of the aquifer is known;
the well loss is known;
the effective aquifer thickness is known.

1− L / b  b
 ln − G( L / b) 
L / b  rw

In most cases, the storage coefficient, well loss, and aquifer thickness can only be estimated. The error introduced is non-negligible, but can be loosely
bracketed. The diagnostic section of the worksheet includes a limited sensitivity analysis.
If the user has little control on well loss, or aquifer thickness, the well loss and partial penetration correction terms may be removed, respectively, by setting the
well loss coefficient (C) equal to zero, and the aquifer thickness (b) equal to the saturated screen interval. Note that the partial penetration correction factor
assumes isotropic conditions (Kh = Kz), and gives a value of T extrapolated from the screened interval to the full aquifer thickness. If the aquifer is anisotropic,
this correction is inappropriate.
b - aquifer thickness
sm - measured drawdown
C - well loss coefficient
sw - well loss
L - screen length
sp - partial penetration parameter
Q - mean pumping rate
rw - effective radius
S - storativity
T - transmissivity
t - pumping duration
Usage Notes
Units
The user may chose any combination of units for field data, estimated parameters and calculated results by
changing the units shown in the column headers. Each of these cells has an embedded pull down list from which to
chose. Only the listed options will work, because the embedded functions look for specific text strings. The units of
the diagnostic columns are linked to the calculated results, and shouldn't be manually changed.
Input
Field data may be pasted in or entered directly. The units header should be changed to agree with the data. All
depth values are assumed to be from a common reference point (e.g., ground surface).
Calculated Results
The calculated results cells all make use of user-defined functions written in Visual Basic for Applications. The
functions and their arguments are listed to the right. The code may be viewed by opening Excel's Visual Basic
Editor. Cells containing these functions may be drag-filled or copied down their respective columns to extend the
table. Changing the units in the column header will automatically change the output units.
Diagnostics
The difference between calculated drawdown the measured drawdown is a metric for assessing the convergence of
the solution. If the error is unacceptably high, the maximum iterations and error tolerance may be adjusted in the
fields above the table. The well bore storage test checks that the specific capacity test rate and duration were
adequate to negate the influence of water removed from the well casing on the measured drawdown. The test
applies criterion that the test duration be longer than 25*rw2/T (ASTM, 2004). Note that this check assumes well
radius and riser radius are equal.
The worksheet assesses the sensitivity of transmissivity to variation in the storage coefficient (S), to the degree of
well loss (sw), and to the effective isotropic aquifer thickness (b). The resulting values shown indicate the variance
of T from the actual estimate, when the target parameter is adjusted as indicated.
Functions and arguments employed in this workbook
CalcDD(TGuess(well diam., diam. units, t, t units, Q, Q units, S, sw, sw units, sp, T, T units, output units)
Returns drawdown calculated from an estimated T.
Getdd(dtw initial, dtw initial units, dtw final, dtw final units, output units)
Returns drawdown calculated from measured depth to water (dtw)
GetK(T, T units, b, b units, output units)
Returns an estimate of hydraulic conductivity calculated by T/b.
Getloss(Q, Q units, C, C units, output units)
Returns the well loss correction factor (s w ).
Getsl(screen top depth, screen top depth units, screen bottom depth, screen bottom depth units, dtw init., dtw units, output units)
Returns the saturated screen length computed from field data.
GetSpCap(Q, Q units, sm, sm units, output units)
Returns specific capacity.
ppen(L, L units, b, b units, d, d units)
Returns the partial penetration correction factor (s p ).
TGuess(well diam., diam. units, sm, sm units, t, t units, Q, Q units, S, sw, sw units, sp, error tolerance, error units, max. steps, output units)
Return an estimate of transmissivity.
wellstorage(well diam., diam. units, t, t units, T, T units)
Returns the text "pass" or "fail" based on a test for inappropriate effects of well bore storage.
References
1) Bradbury, K.B., and E.R. Rothschild, 1985. A computerized technique for estimating the hydraulic conductivity of aquifer from
specific capacity data: Ground Water vol. 23, No. 2, pp. 240-246.
2) ASTM International, 2004. Standard Test Method for Determining Specific Capacity and Estimating Transmissivity at the Control
Well, Standard D 5472-93, in Annual Book of ASTM Standards, Vol. 04.08 pp. 1279-1282.
Questions/Bugs, contact:
Michael Cobb, UW-Madison Department of Geology and Geophysics, [email protected]
>
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>
!
00219508
>
!
00217922
>
!
00112244
2
1
>
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;
!
N
0
North Branch Wells
>
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Other Wells - County Well Index
Feet
100 200 300 400
Fond du Lac Aquifer Wells
North Branch Water and Light
Appendix C
MDH Well Vulnerability Assessments
Appendix D
Summary of Fracture Flow Capture Zone Calculations
Well 1 (unique #217922)
Calculation for Ratio of Well Discharge to the Discharge Vector (Q/Qs)
See: Appendix 2 of Guidance for Delineating Wellhead Protection Area in Fractured and Solution-Weathered Bedrock in Minnesota (MDH, 2005)
If Q/Qs is less than 3000 m then delineation Technique 2 should be used: Calculated Fixed Radius with An Upgradient Extension
Input variables
Well Discharge, Q (gpm)
Aquifer Thickness, H (ft)
Aquifer Hydraulic Conductivity K (m/day)
Hydraulic Gradient, i
304
200
1.3
0.0037191
Calculated Q/Qs (m)
5623
Equation listed in Appendix 2 of Guidance
for Delineating Wellhead Protection Area in
Fractured and Solution-Weathered Bedrock
in Minnesota (MDH, 2005)
 1 ft 3  1440 min  0.0283m 3


Q
7.48 gal  1day  1 ft 3

Q / Qs =
(H ) 0.3048m (K )(i )
 1 ft 



Calculation for Fixed Radius with No Upgradient Extension
See method 1 of Guidance for Delineating Wellhead Protection Area in Fractured and Solution-Weathered Bedrock in Minnesota (MDH, 2005)
Input Variables
Well Pumping Rate m3/day
Pumping Period (years)
Effective porosity, n
Thickness of saturated portion of aquifer, L
(m)
R=
1657
10
0.1
61.0
Q
nLπ
Where:
Q = Well Discharge (L 3/T)=(Well pumping rate)(pumping time period)
n = effective porosity
L = thickness of saturated portion of aquifer (L) note: lesser of open borehole or 200 ft
Calculated Fixed Radius (m)
562
Volume (m3)
60,493,520
Well 2 (unique #112244)
Calculation for Ratio of Well Discharge to the Discharge Vector (Q/Qs)
See: Appendix 2 of Guidance for Delineating Wellhead Protection Area in Fractured and Solution-Weathered Bedrock in Minnesota (MDH, 2005)
If Q/Qs is less than 3000 m then delineation Technique 2 should be used: Calculated Fixed Radius with An Upgradient Extension
Input variables
Well Discharge, Q (gpm)
Aquifer Thickness, H (ft)
Aquifer Hydraulic Conductivity K (m/day)
Hydraulic Gradient, i
95
99
1.3
0.0037191
Calculated Q/Qs (m)
3560
Equation listed in Appendix 2 of Guidance
for Delineating Wellhead Protection Area in
Fractured and Solution-Weathered Bedrock
in Minnesota (MDH, 2005)
 1 ft 3  1440 min  0.0283m 3


Q
7.48 gal  1day  1 ft 3

Q / Qs =
(H ) 0.3048m (K )(i )
 1 ft 



Calculation for Fixed Radius with No Upgradient Extension
See method 1 of Guidance for Delineating Wellhead Protection Area in Fractured and Solution-Weathered Bedrock in Minnesota (MDH, 2005)
Input Variables
Well Pumping Rate m3/day
Pumping Period (years)
Effective porosity, n
Thickness of saturated portion of aquifer, L
(m)
R=
519
10
0.1
30.2
Q
nLπ
Where:
Q = Well Discharge (L 3/T)=(Well pumping rate)(pumping time period)
n = effective porosity
L = thickness of saturated portion of aquifer (L) note: lesser of open borehole or 200 ft
Calculated Fixed Radius (m)
447
Volume (m3)
18,957,217
Well 3 (unique #522767)
Calculation for Ratio of Well Discharge to the Discharge Vector (Q/Qs)
See: Appendix 2 of Guidance for Delineating Wellhead Protection Area in Fractured and Solution-Weathered Bedrock in Minnesota (MDH, 2005)
If Q/Qs is less than 3000 m then delineation Technique 2 should be used: Calculated Fixed Radius with An Upgradient Extension
Input variables
Well Discharge, Q (gpm)
Aquifer Thickness, H (ft)
Aquifer Hydraulic Conductivity K (m/day)
Hydraulic Gradient, i
246
118
10.9
0.0023265
Calculated Q/Qs (m)
1470
Equation listed in Appendix 2 of Guidance
for Delineating Wellhead Protection Area in
Fractured and Solution-Weathered Bedrock
in Minnesota (MDH, 2005)
 1 ft 3  1440 min  0.0283m 3


Q
7.48 gal  1day  1 ft 3

Q / Qs =
(H ) 0.3048m (K )(i )
 1 ft 



Calculation for Fixed Radius with No Upgradient Extension
See method 1 of Guidance for Delineating Wellhead Protection Area in Fractured and Solution-Weathered Bedrock in Minnesota (MDH, 2005)
Input Variables
Well Pumping Rate m3/day
Pumping Period (years)
Effective porosity, n
Thickness of saturated portion of aquifer, L
(m)
R=
1340
5
0.233
36.0
Q
nLπ
Where:
Q = Well Discharge (L 3/T)=(Well pumping rate)(pumping time period)
n = effective porosity
L = thickness of saturated portion of aquifer (L) note: lesser of open borehole or 200 ft
Calculated Fixed Radius (m)
305
Volume (m3)
10,499,079
Well 4 (unique #706844)
Calculation for Ratio of Well Discharge to the Discharge Vector (Q/Qs)
See: Appendix 2 of Guidance for Delineating Wellhead Protection Area in Fractured and Solution-Weathered Bedrock in Minnesota (MDH, 2005)
If Q/Qs is less than 3000 m then delineation Technique 2 should be used: Calculated Fixed Radius with An Upgradient Extension
Input variables
Well Discharge, Q (gpm)
Aquifer Thickness, H (ft)
Aquifer Hydraulic Conductivity K (m/day)
Hydraulic Gradient, i
155
60
10.9
0.0023265
Calculated Q/Qs (m)
1824
Equation listed in Appendix 2 of Guidance
for Delineating Wellhead Protection Area in
Fractured and Solution-Weathered Bedrock
in Minnesota (MDH, 2005)
 1 ft 3  1440 min  0.0283m 3


Q
7.48 gal  1day  1 ft 3

Q / Qs =
(H ) 0.3048m (K )(i )
 1 ft 



Calculation for Fixed Radius with No Upgradient Extension
See method 1 of Guidance for Delineating Wellhead Protection Area in Fractured and Solution-Weathered Bedrock in Minnesota (MDH, 2005)
Input Variables
Well Pumping Rate m3/day
Pumping Period (years)
Effective porosity, n
Thickness of saturated portion of aquifer, L
(m)
R=
846
5
0.233
18.3
Q
nLπ
Where:
Q = Well Discharge (L 3/T)=(Well pumping rate)(pumping time period)
n = effective porosity
L = thickness of saturated portion of aquifer (L) note: lesser of open borehole or 200 ft
Calculated Fixed Radius (m)
340
Volume (m3)
6,625,374
Well 5 (unique #749383)
Calculation for Ratio of Well Discharge to the Discharge Vector (Q/Qs)
See: Appendix 2 of Guidance for Delineating Wellhead Protection Area in Fractured and Solution-Weathered Bedrock in Minnesota (MDH, 2005)
If Q/Qs is less than 3000 m then delineation Technique 2 should be used: Calculated Fixed Radius with An Upgradient Extension
Input variables
Well Discharge, Q (gpm)
Aquifer Thickness, H (ft)
Aquifer Hydraulic Conductivity K (m/day)
Hydraulic Gradient, i
25
138
10.9
0.0007754
Calculated Q/Qs (m)
386
Equation listed in Appendix 2 of Guidance
for Delineating Wellhead Protection Area in
Fractured and Solution-Weathered Bedrock
in Minnesota (MDH, 2005)
 1 ft 3  1440 min  0.0283m 3


Q
7.48 gal  1day  1 ft 3

Q / Qs =
(H ) 0.3048m (K )(i )
 1 ft 



Calculation for Fixed Radius with No Upgradient Extension
See method 1 of Guidance for Delineating Wellhead Protection Area in Fractured and Solution-Weathered Bedrock in Minnesota (MDH, 2005)
Input Variables
Well Pumping Rate m3/day
Pumping Period (years)
Effective porosity, n
Thickness of saturated portion of aquifer, L
(m)
R=
137
5
0.233
42.1
Q
nLπ
Where:
Q = Well Discharge (L 3/T)=(Well pumping rate)(pumping time period)
n = effective porosity
L = thickness of saturated portion of aquifer (L) note: lesser of open borehole or 200 ft
Calculated Fixed Radius (m)
90
Volume (m3)
1,076,083
Well 6 (unique #593584)
Calculation for Ratio of Well Discharge to the Discharge Vector (Q/Qs)
See: Appendix 2 of Guidance for Delineating Wellhead Protection Area in Fractured and Solution-Weathered Bedrock in Minnesota (MDH, 2005)
If Q/Qs is less than 3000 m then delineation Technique 2 should be used: Calculated Fixed Radius with An Upgradient Extension
Input variables
Well Discharge, Q (gpm)
Aquifer Thickness, H (ft)
Aquifer Hydraulic Conductivity K (m/day)
Hydraulic Gradient, i
40
110
1.3
0.0034836
Calculated Q/Qs (m)
1433
Equation listed in Appendix 2 of Guidance
for Delineating Wellhead Protection Area in
Fractured and Solution-Weathered Bedrock
in Minnesota (MDH, 2005)
 1 ft 3  1440 min  0.0283m 3


Q
7.48 gal  1day  1 ft 3

Q / Qs =
(H ) 0.3048m (K )(i )
 1 ft 



Calculation for Fixed Radius with No Upgradient Extension
See method 1 of Guidance for Delineating Wellhead Protection Area in Fractured and Solution-Weathered Bedrock in Minnesota (MDH, 2005)
Input Variables
Well Pumping Rate m3/day
Pumping Period (years)
Effective porosity, n
Thickness of saturated portion of aquifer, L
(m)
R=
218
5
0.1
33.5
Q
nLπ
Where:
Q = Well Discharge (L 3/T)=(Well pumping rate)(pumping time period)
n = effective porosity
L = thickness of saturated portion of aquifer (L) note: lesser of open borehole or 200 ft
Calculated Fixed Radius (m)
194
Volume (m3)
3,972,162
Wells 1 and 2
Calculation of Revised Volume for Overlapping Capture Zones
See: Section 5, Scenario 1 of Guidance for Delineating Wellhead Protection Area in Fractured and Solution-Weathered Bedrock in Minnesota (MDH, 2005)
Well
Fixed Radius (m)
1
2
Open Hole (m)
562
447
61
30.2
Top of open hole (ft)
Bottom of open hole (ft)
Overlap
263
463 261
360 0.979798
Contributing Well 2 volume
3
60533213.96 m
3
18589508.06 m
Total Volume
3
79122722.03 m
Well 1 volume
Revised Radius
643 m
Wells 1,2 and 6
Calculation of Revised Volume for Overlapping Capture Zones
See: Section 5, Scenario 2 of Guidance for Delineating Wellhead Protection Area in Fractured and Solution-Weathered Bedrock in Minnesota (MDH, 2005)
Well
Fixed Radius (m)
1,2
6
Open Hole (m)
643
194
Overlap area
Common Open Hole Interval
Overlap volume
Well 1,2 volume
Well 6 volume
1,2 Overlap
6 Overlap
Revised Well 1,2 Volume
Revised Well 6 Volume
Revised Well 1,2 Radius
Revised Well 6 Radius
61
33.5
2
113041.88 m
33.5 m
3
3786903 m
3
79122722.03 m
3
3960938.867 m
3
3606365.784 m
3
180537 m
3
82729087.81 m
3
4141476 m
657 m
198 m
10 Year Fixed Radius Capture Zone Up Gradient Extensions
Well 3
522767
Well Location
X
Y
Length of extension (1.57 *
radius of fixed radius capture
zone)
Flow Direction
Flow Direction + 10 degrees
Flow Direction - 10 degrees
Well 4
500198
5039362
Center of extension
X
Y
478.5769999
Center of extension +10 degrees
-101.2
-91.2
-111.2
X
Y
Center of extension - 10 degrees
X
Y
499728.5
5039269
499719.5
5039352
499751.8
5039189
706844
Well Location
X
Y
Length of extension (1.57 *
radius of fixed radius capture
zone)
Flow Direction
Flow Direction + 10 degrees
Flow Direction - 10 degrees
499154
5038991
533.1467837
-101.2
-91.2
-111.2
Center of extension
X
Y
Center of extension +10 degrees
X
Y
Center of extension - 10 degrees
X
Y
498631
5038887
498621
5038980
498656.9
5038798
10 Year Fixed Radius Capture Zone Up Gradient Extensions
Well 5
749383
Well Location
X
Y
Length of extension (1.57 *
radius of fixed radius capture
zone)
Flow Direction
Flow Direction + 10 degrees
Flow Direction - 10 degrees
Well 6
498446
5039147
141.6774185
-104.2
-94.2
-114.2
Center of extension
X
Y
Center of extension +10 degrees
X
Y
Center of extension - 10 degrees
X
Y
498308.7
5039112
498304.7
5039137
498316.8
5039089
593584
Well Location
X
Y
Length of extension (1.57 *
radius of fixed radius capture
zone)
Flow Direction
Flow Direction + 10 degrees
Flow Direction - 10 degrees
501930
5039325
311.4439439
-137.4
-127.4
-147.4
Center of extension
X
Y
Center of extension +10 degrees
X
Y
Center of extension - 10 degrees
X
Y
501719.2
5039096
501682.6
5039136
501762.2
5039063
Appendix E
Groundwater Model
Figure E1
Observed vs Computed Hydraulic Head
Entire Model
320
Simulated (m)
300
280
Mean Residual = -2.7 m
Std. Dev. = 5.3 m
Min. Residual = -28.0 m
Max. Residual = 24.4 m
Std. Dev. / Range = 0.1 m
260
240
220
220
240
260
280
Observed (m)
300
320
North Branch Area
290
280
Simulated (m)
270
260
Mean Residual = -1.2 m
Std. Dev. = 5.4 m
Min. Residual = -19.0 m
Max. Residual = 12.7 m
Std. Dev. / Range = 0.1 m
250
240
230
230
240
250
260
270
Observed (m)
280
290
Figure E2
Parameter Sensitivities
Kx8
4.0000E+05
3.9500E+05
Kx3
3.9000E+05
Kz3
Kx1
3.6500E+05
3.6000E+05
Parameter
Kz12
Kz11
Kz10
Kz9
Kz8
Kz7
Kz6
Kz4
Kz5
3.7000E+05
Kz2
Kz1
Kx12
Kx11
Kx10
Kx7
Kx6
3.7500E+05
Kx4
Kx5
Kx9
3.8000E+05
Kx2
Sensitivity
3.8500E+05
Groundwater Modeling Evaluation of Future Wells for the North
Branch Water and Light Commission
Prepared for:
WSB and Associates, Inc.
November 2005
Table of Contents
Introduction ................................................................................................................................................... 1
1.1 Purpose and Scope ...................................................................................................................... 1
1.2 Summary of Findings .................................................................................................................. 1
2 Groundwater Flow Model Development ................................................................................................... 3
2.1 What is a Groundwater Flow Model? ......................................................................................... 3
2.2 Overview of Steps to Building and Using the Groundwater Flow Model .................................. 3
2.3 Conceptual Hydrogeologic Model .............................................................................................. 4
2.3.1 Statement of Problem Evaluated .................................................................................... 5
2.3.2 Geologic Conditions, Aquifers, and Aquitards .............................................................. 5
2.3.3 Summary of Conceptual Hydrogeologic Model ............................................................ 7
2.4 Groundwater Flow Model Construction ..................................................................................... 8
2.4.1 Model Domain and Horizontal Discretization ............................................................... 8
2.4.2 Vertical Discretization ................................................................................................... 8
2.4.3 Layer Geometry and Base Elevations ............................................................................ 8
2.4.4 Hydraulic Conductivity Zonation .................................................................................. 9
2.4.5 Faults .............................................................................................................................. 9
2.4.6 Lakes and Rivers ............................................................................................................ 9
2.4.7 Recharge ........................................................................................................................ 9
2.4.8 Wells .............................................................................................................................. 9
2.5 Model Calibration ..................................................................................................................... 10
2.5.1 Overview of Calibration Process ................................................................................. 10
2.5.2 Calibration Targets....................................................................................................... 10
2.5.3 Calibration Results ....................................................................................................... 11
2.5.4 Sensitivity and Uncertainty .......................................................................................... 11
3 Predictive Simulations of Future Well Locations .................................................................................... 12
3.1 Design Considerations .............................................................................................................. 12
3.2 Well Location Alternative Evaluation ...................................................................................... 13
3.2.1 Well Alternative 1 ........................................................................................................ 13
3.2.2 Well Alternative 2 ........................................................................................................ 13
3.2.3 Well Alternative 3 ........................................................................................................ 13
3.3 Discussion of Well Alternatives ............................................................................................... 14
3.3.1 Well Capacity and Drawdown at the Wells ................................................................. 14
3.3.2 Regional Drawdown Effects ........................................................................................ 14
i
Table of Contents (continued)
3.2.3
Effect of Nearby Fault System ..................................................................................... 15
4 Considerations for Future Well Siting ..................................................................................................... 16
4.1 Test Drilling and Test Wells ..................................................................................................... 16
4.2 Appropriations Permits ............................................................................................................. 16
4.3 Wellhead Protection Area Delineation ..................................................................................... 17
References ................................................................................................................................................... 18
ii
List of Figures
Figure 1
Uppermost Bedrock Interpreted from County Well Index Data
Figure 2
Approximate Depth to Bedrock (feet)
Figure 3
Conceptual Model of Groundwater Flow
Figure 4
Model Domain and Horizontal Grid Discretization
Figure 5
Cross Sections Through Model Depicting Vertical Discretization
Figure 6
Example of Zonation for Hydraulic Conductivity
Figure 7
Wall Feature, Representing Fault Boundary
Figure 8
Recharge Zones in the Model
Figure 9
Wells in Model
Figure 10 Plot of Observed and Simulated Observations
Figure 11 Contours of Simulated Potentiometric Head (feet, above mean sea level)for Layer 4 (Mt.
Simon-Hinckley Aquifer)
Figure 12 Relative Sensitivity of Model Calibration to Parameters
Figure 13 Well Alternative 1: Predicted Drawdown (feet) in Mt. Simon-Hinckley Aquifer
Figure 14 Well Alternative 1: Predicted Drawdown (feet) in Franconia-Ironton-Galesville Aquifer
Figure 15 Well Alternative 1: Predicted Drawdown (feet) in Water-Table Aquifer
Figure 16 Well Alternative 2: Predicted Drawdown (feet) in Mt. Simon-Hinckley Aquifer
Figure 17 Well Alternative 2: Predicted Drawdown (feet) in Franconia-Ironton-Galesville Aquifer
Figure 18 Well Alternative 2: Predicted Drawdown (feet) in Water-Table Aquifer
Figure 19 Well Alternative 3: Predicted Drawdown (feet) in Mt. Simon-Hinckley Aquifer
iii
Table of Contents (continued)
Figure 20 Well Alternative 3: Predicted Drawdown (feet) in Franconia-Ironton-Galesville Aquifer
Figure 21 Well Alternative 3: Predicted Drawdown (feet) in Water-Table Aquifer
iv
Introduction
1.1
Purpose and Scope
This report summarizes the results of a study to identify and predict the location of future water
supply wells for the North Branch Water and Light Commission. Recent attempts within the City
limits to install wells have been met with limited success, due mainly to the caving in of the openhole section of the well. Previous evaluation of the geologic setting (Letter to Nancy Zeigler from
Brian LeMon and John Greer, September 15, 2005) suggests that there is a Precambrian fault system
underneath North Branch that uplifted the bedrock, causing significant thinning of the Mt. SimonHinckley aquifer and fracturing of the bedrock. That study, and supplemental work performed as part
of this study, indicates that the fault system is likely underneath and parallel to Interstate 35.
This study suggests that just to the west of the City limit, the full section of the Mt. Simon -Hinckley
aquifer, as well as the overlying Eau Claire Formation and the Franconia-Ironton-Galesville aquifer,
should be present. The uplifted fault block (horst) is primarily east of the City’s western limit.
Therefore, new wells should be installed west of the City in the Mt. Simon-Hinckley aquifer and also
possibly in the Franconia-Ironton-Galesville aquifer.
A regional three-dimensional groundwater flow model was developed to evaluate locations for five
future wells, each pumping at 900 gallons per minute (gpm). Four to five additional wells should be
able to supply future water demand. The groundwater flow model was calibrated and used to estimate
the drawdown that would be caused by pumping of these wells.\
1.2
Summary of Findings
This study finds the following:
1. A new well field could be developed approximately two miles west of the City. Wells
installed in the Mt. Simon-Hinckley aquifer and in the Franconia-Ironton-Galesville aquifer
should be able to yield sufficient quantities of groundwater.
2. These new wells will cause regional drawdown, as expected. Some existing wells in the area
might experience some drops in yield but it is likely that there would be no noticeabl e
adverse impacts from pumping.
1
3. The fault system does not appear to adversely affect well yields, provided that the wells are
installed sufficiently west of the City to encounter the Franconia-Ironton-Galesville aquifer
and the full section of the Mt. Simon-Hinckley aquifer. While two miles west of the City
limits should be sufficient, test drilling and pumping tests should be performed to verify this
conclusion.
2
2 Groundwater Flow Model Development
2.1
What is a Groundwater Flow Model?
A groundwater flow model is a computer program that simulates the important conditions that
control groundwater levels, flow to wells, and the interactions between geology and surface -water
features. The computer program uses well-established mathematical equations that describe how
water flows in aquifers and aquitards. The program is tailored to a particular area’s geology and
hydrology and is, most importantly, formulated to answer very specific problems.
For this study, the groundwater flow code MODFLOW was used (McDonald and Harbaugh, 1988).
MODFLOW was developed by the U.S. Geological Survey and is the most widely used groundwater
modeling code in the world. MODFLOW employs a finite-difference method of solving the
differential equations that describe groundwater flow. It is capable of simulating three-dimensional
flow in aquifers and aquitard, both in steady-state and transient modes.
Graphical user interfaces (GUIs) are almost always used with groundwater flow models. GUIs
greatly assist in designing the model, entering the data, and post-processing the results. For this
study, the GUI Groundwater Vistas, version 4 (ESI, 2004) was used.
2.2 Overview of Steps to Building and Using the Groundwater
Flow Model
The groundwater flow model for this study was developed in the following steps:
1. The hydrogeology and data availability of the area was evaluated and summarized (Letter to
Nancy Zeigler from Brian LeMon and John Greer, September 15, 2005). The most salient
feature in the study area is fault block (horst) underneath the City of North Branch that has
lifted up the Franconia-Ironton-Galesville aquifer and the Mt. Simon-Hinckley aquifer and
subsequently eroded these units away (or thinned them considerably).
2. The problems that require a groundwater flow model were determined. In this case, the
problem at hand is to determine where wells can be installed to the west of the City of North
Branch in order to maximize well yields and meet future water demands.
3
3. A conceptual model of groundwater flow was developed. The conceptual model is a
schematic representation of the major aquifers, aquitards, water sources, and water sinks in
the area. The conceptual model is the basis for the computer model of groundwater flow.
4. The computer model was built using the following information:
a. Elevations of the base of key hydrostratigraphic units from the Minnesota Geological
Survey’s County Well Index (CWI);
b. Surface-water features, including lake stage elevation;
c. Higher capacity wells (i.e. wells with groundwater appropriations permits), with
pumping rates assigned on the basis of 2004 annual averages; and
d. Geophysical data on the locations of fault zones.
5. The computer model is put through an exhaustive calibration procedure to “ground truth” the
model and prepare it for predictive simulations. The calibration process involves
automatically adjusting model parameters (e.g., aquifer and aquitard hydraulic conductivity
and recharge from infiltrating precipitation) with expected ranges until the difference
between groundwater levels measured in wells (from CWI) and the computer’s simulation of
groundwater levels is minimized in a least-squares sense. In other words, the calibration
process ensures that the model is capable of reasonably reproducing current groundwater
flow conditions.
The calibrated groundwater flow model becomes a tool for predicting the effects of future wells. The
model can be used to predict the amount of drawdown induced by a given pumping rate for future
well locations and thereby make some conclusions about well interference effects, potential yields,
and optimal spacing between future wells. Thus, the groundwater flow model becomes the design
tool for a new well field.
2.3
Conceptual Hydrogeologic Model
The conceptual hydrogeologic model defines the major aquifers, aquitards, geologic structures, and
water sources/sinks that are important to the location and the problem for which the model is being
developed. The conceptual model establishes how geologic units interact with hydrologic features to
control the direction and rate of groundwater flow. The conceptual model also forms the basis for
4
how aquifers and aquitards are represented in the computer model (i.e. how geologic units are
lumped together or split apart for the purposes of the computer simulation.
2.3.1 Statement of Problem Evaluated
Different conceptual models may be necessary for a particular location, depending upon the nature of
the problem(s) that the computer model is intended to evaluate. Once built, a compute model may be
able to solve other problems for which it was not originally designed but often a new model with a
different conceptual model may be necessary.
The problem for which this model was developed is stated as follows:
Locations for new public water supply wells for the North Branch Water and Light Commission
will be evaluated with the model. The area of focus is immediately west of the City and west of a
known fault zone. The primary aquifer of interest is the Mt. Simon-Hinckley aquifer. An aquifer
of secondary interest is the Franconia-Ironton-Galesville (FIG) aquifer. The following questions
may need addressing:
1. How close to the fault zone can a well be located before boundary effects impinge upon the
well’s yield?
2. What are reasonable expectations for well yield?
3. If wells are located to meet expected future demands, where should those wells be located (in
particular, how far apart should these wells be located to minimize well interference effects)?
4. How much will groundwater levels be lowered in the area and what existing wells in the area
might be affected by pumping of new municipal water supply wells?
2.3.2 Geologic Conditions, Aquifers, and Aquitards
2.3.2.1 Geologic History
North Branch is located in the northern part of a geologic feature called the Hollandale Embayment –
a large bay in an ancient shallow sea were sediment was deposited as the seas waxed and waned to
form what is now most of the major bedrock geologic units in eastern Minnesota. Before the
deposition of what is now the Mt. Simon Sandstone, there was structural uplifting of Precambrian
rocks that formed an uplifted block (called a “horst”) that trends north-south. The western edge of
5
this horst corresponds approximately with Interstate 35. Subsequent tectonic activities formed a
structural basin (the Twin Cities basin), centered under what is now Minneapolis and St. Paul.
Bedrock units generally dip southward toward the center of the Twin Cities basin. There may have
been some reactivation of the Precambrian faults after deposition of younger rocks (Morey, 1972).
During the Quaternary (about the last two-million years), glacial advances eroded away higher relief
bedrock units and deposited a mixture of glacially derived tills and outwash over the landscape. The
combination of depositional history, structural faulting, and glaciation has resulted in the current
geologic setting. Major bedrock aquifer units, such as the Prairie du Chien-Jordan aquifer, are not
present in the North Branch area, due to these processes. The Franconia-Ironton-Galesville aquifer is
present to west of North Branch but underneath North Branch (where the underlying horst feature is
present), the uppermost bedrock unit is the Mt. Simon Sandstone (and the upper portion of this unit
has also been eroded).
2.3.2.2 Regional Bedrock Geology
A definitive published map of the uppermost bedrock in the North Branch area and surrounding
region is not available. County Well Index data were evaluated to identify the uppermost bedrock
unit in wells in the region. Differentiation between units, especially with respect to Mt. Simon
Sandstone, Hinckley Formation, and Fond du Lac Formation is difficult in some locations, based on
the drilling logs. An interpretation of the approximate extent of uppermost bedrock units is shown on
Figure 1. Also shown on this figure is the approximate location of the horst, as interpreted from the
Minnesota Geological Survey’s aeromagnetic survey results (included as part of Letter to Nancy
Zeigler from Brian LeMon and John Greer, September 15, 2005). The depth to bedrock is greatest in
the vicinity of the horst feature underneath North Branch. The interpreted depth to bedrock, based on
CWI data, is shown on Figure 2.
2.3.2.3 Hydrostratigraphy
Hydrostratigraphy refers to the geologic units that make up aquifers and aquitards. Aquifers transmit
usable quantities of water, whereas aquitards do not. Aquitards typically separate one aquifer from
another and are sometimes referred to as “confining beds”.
Hydrostratigraphic units that are considered as part of the groundwater model in the evaluation of
water supplies for North Branch include:
6
Geologic Unit
Hydrostratigraphic Unit
Comments
Quaternary glacial sediments
Surficial Aquifer
Locally variable; susceptible to
contamination
Franconia Formation
Franconia-Ironton-Galesville
(FIG) Aquifer
May have yields high enough
for public water supplies
Eau Claire Formation
Eau Claire Aquitard
Significant regional aquitard
Mt. Simon and Hinckley
Sandstones
Mt. Simon-Hinckley Aquifer
Moderately high yields where
full section is present; may have
high total dissolved solids
Fond du Lac Formation
Fond du Lac Aquifer
Moderate to poor yield; high
total dissolved solids
Ironton & Galesville
Sandstones
2.3.2.4 Recharge and Discharge of Groundwater
The primary mechanisms of recharge to the aquifer system in the region is infiltrating precipitation
that moves below the root zone of plants and migrates downward by gravity to the water table.
Recharge rates in east-central Minnesota are typically in the range of less than 1 inch per year to over
12 inches per year. A secondary source of recharge is seepage through the bottoms of lakes,
wetlands, and some streams.
Most groundwater flows southeast and east toward the St. Croix River, which is a regional discharge
zone. Secondary discharge zones includes smaller streams, some lakes and wetlands,
evapotranspiration from plants, and wells.
2.3.2.5 Direction of Groundwater Flow
Regional groundwater flow is to the east and south, toward the St. Croix River. Differing directions
of flow can be expected for the shallow aquifer (surficial deposits) near lakes and streams. Near high
capacity wells, groundwater flow is typically toward the wells.
2.3.3 Summary of Conceptual Hydrogeologic Model
The conceptual hydrogeologic model of groundwater flow in the region is depicted schematically in
the cross section on Figure 2. The conceptual model consists of five hydrostratigraphic units
7
(surficial aquifer; Franconia-Ironton-Galesville aquifer; Eau Claire aquitard; Mt. Simon-Hinckley
aquifer; and Fond du Lac aquifer).
2.4
Groundwater Flow Model Construction
2.4.1 Model Domain and Horizontal Discretization
The domain (extent) of the groundwater flow model is shown on Figure 4. Also shown on Figure 4 is
the finite-difference grid. The domain was selected to encompass an area sufficiently large enough to
include the major hydraulic sources and sinks. The western boundary of the model represents the
approximate western extent of the Mt. Simon-Hinckley aquifer. The eastern edge extends to the St.
Croix River.
The model is approximately 94 km x 67 km. There are 103 rows and 148 columns, with 60,800 active
grid cells. The maximum grid cell size is 1 km x 1 km (for far-field areas where model accuracy is
not as important). The grid is refined in areas west of North Branch, were predictive simulations of
future wells are performed. Grid cells in this area are a maximum of 250 m x 250 m, and are refined
much smaller around hypothetical wells for predictive simulations.
2.4.2 Vertical Discretization
The model is divided into five computation layers. Layer 1 represents the glacial drift aquifer. Layer
2 is generally the Franconia-Ironton-Galesville aquifer. Layer 3 is generally the Eau Claire aquitard.
Layer 4 is the Mt. Simon-Hinckley aquifer and Layer 5 is the Fond du Lac aquifer. Along the
periphery of the model domain and where the Franconia-Ironton-Galesville aquifer and/or the Eau
Claire aquitard are not present, Layers 2 and 3 also can represent portions of the Mt. Simon -Hinckley
aquifer.
2.4.3 Layer Geometry and Base Elevations
Base elevations for the various layers were assigned using well log information in the County Well
Index. These data were geostatistically assigned to grid cells in the model domain for the various
layers. Cross sections through the model are shown on Figure 5, depicting the vertical discetization
and the variation in model layers across the model domain. In the vicinity of North Branch, where
faulting of the horst has increased the relative elevation of bedrock units, the model’s base is
substantially higher and layers are thinner.
8
2.4.4 Hydraulic Conductivity Zonation
There is almost no regional data on hydraulic conductivity (permeability) values for the bedrock
units in the model domain. Information from the Twin Cities area provides some guidance. The
approach used in this study was to determine the aquifer parameter values through an inverse
optimization method in the calibration process. This process lends itself to dividing up the model
layers into zones where hydraulic conductivity values are likely to be similar. For exa mple, in Layer
2, there are zones to delineate where the Franconia Ironton-Galesville is present, zones for where the
Eau Claire Formation is present, and zones for glacial drift. Examples of zonation are shown on
Figure 6. Each zone has both a horizontal and a vertical hydraulic conductivity value.
2.4.5 Faults
The fault system that is associated with the horst feature is represent in two ways: by varying the
base elevation of the bottom of the Fond du Lac Formation and by including horizontal wall features
that have lower values of hydraulic conductivity. The horizontal wall features hinder groundwater
flow across the fault zone. They are included in all five layers of the model, at the location shown on
Figure 7.
2.4.6 Lakes and Rivers
Major lakes and rivers are represented in the model using constant head cells, for which the average
lake stage is assigned (in meters above mean sea level). Average lake stages were obtained from the
Minnesota Department of Natural Resources Lakefinder web site. All lakes are in Layer 1, except
portions of the St. Croix River, which are in both Layers 1 and 2.
2.4.7 Recharge
Recharge is applied to Layer 1. Recharge represents the average annual rate of water that infiltrates
through the ground and reaches the water table. Recharge is divided into zones in the model for
calibration. Recharge zones are shown on Figure 8. Recharge zones correspond approximately to
hydraulic conductivity zones in Layer 1.
2.4.8 Wells
High capacity pumping wells are included in the model if they are listed in the Minnesota
Department of Natural Resources SWUDS data base for 2004. These are wells that have groundwater
appropriations permits. There are 84 pumping wells in the model. Pumping rates assigned to the
9
wells are the average annual rates for 2004, converted to cubic meters per day. Depending on the
length of the well screen or open-hole interval, wells may penetrate multiple layers. Wells in the
model are shown on Figure 9.
2.5
Model Calibration
2.5.1 Overview of Calibration Process
Model calibration is the process of varying aquifer parameters (e.g., hydraulic conductivity,
recharge) within expected ranges of values until an acceptable match is obtained between observed
groundwater levels in wells and simulated groundwater levels. The observed water levels are called
calibration “targets”. The difference between the observed data and the simulated data is called a
“residual”. The objective of calibration is to minimize the residual.
It is impossible to perfectly match every observation. The objective of calibration is to obtain a
minimum residual for all of the calibration targets. The “objective function”, as it is called, is to
minimize the sum of the squares of all residuals. Residuals are squared to normalize values that
would otherwise be either negative residuals or positive residuals.
An automated calibration method was used in this study. This process is called “automated inverse
optimization” and involves the use of another program, called PEST (Watermark Computing, 1994).
PEST numerically solves for the derivative of the objective function, thereby obtaining the minimum.
The types of parameters, the parameter zones, and the permissible upper and lower limits of the
parameter values are set prior to the optimization process. PEST then runs the groundwater model
several hundred times until the objective function is minimized.
2.5.2 Calibration Targets
In this study, 5,258 calibration targets, representing groundwater elevation data from wells in all
layers were used, with the exception of Layer 3 (Eau Claire aquitard), which does not have wells
completed in it. The calibration targets themselves have associated measurement errors. The
calibration targets used in this study were obtained from the static water elevations listed in the
County Well Index. The sources of error in these data include the following:

Error in measurement by the driller at time that the well was drilled;

Seasonal variations, depending on when the well was drilled;
10

Year-to-year variations, depending on when the well was drilled;

Error in estimating the ground surface elevation of the well;

Error in assigning the well to the correct hydrostratigraphic unit;

Errors caused by local pumping conditions not included in the model.
Despite these errors, CWI calibration data has proven to be very useful. The shear size of the data set
(over 5,000 targets) negates many of the errors.
A weighting process was used to assign more emphasis on certain target values than others. Most of
the targets in the model domain are shallow wells in the glacial drift aquifer. This aquifer is of less
importance to the objectives of this study than bedrock aquifers. Therefore, during the
calibration/optimization process, twice the weight was assigned to bedrock targets than glacial dirft
aquifer targets.
2.5.3 Calibration Results
A plot of the observed and simulated observations is shown on Figure 10. The residual mean is -3.22
meters. The residual standard deviation divided by the range in head over the model domain is 0.063.
Values less than 0.1 are indicative of a good calibration. An example of the calibrated model’s
simulated potentiometric head is shown on Figure 11 for Layer 4 (Mt. Simon-Hinckley aquifer). As
seen in Figure 11, the area of the horst is a location where aquifer transmissivities decrease and
hydraulic head gradient increases. This trend in groundwater levels is similar in all five layers.
2.5.4 Sensitivity and Uncertainty
The model’s results are most sensitive to values of recharge, as shown on Figure 12. This is typical,
because recharge is the primary source of water to the groundwater flow system. Recharge Zone 1,
which is recharge to areas where the Mt. Simon-Hinckley aquifer subcrops beneath glacial drift, is
the most sensitive parameter.
It is important to recognize that the calibrated model represents one possible representation of the
conceptual flow system – there may be others that are equally plausible. As such, there is inherent
uncertainty in the model’s conceptualization, parameter values, and predictive results.
11
3 Predictive Simulations of Future Well Locations
3.1
Design Considerations
For the purpose of evaluating future well locations with the groundwater flow model, it was assumed
that the City of North Branch will need a total of approximately 4,500 gallons per minute (gpm) firm
capacity 18 years from present (2024). This 900 gpm higher than the estimated 3,600 gpm needed but
provides for some additional capacity, beyond the estimated future needs. The predictive simulations
assume that this demand will be met by 5 wells, each pumping at 900 gpm. These five wells would
be located in an area west of the City limits and west of the area where faulting is believed to be
prevalent. It was also assumed that the five wells would be serviced by a single raw water main
connecting the wells to treatment within the City limits.
The length of raw water main could be a limiting factor (e.g., cost, accessibility, etc.). The alternative
well locations that are evaluated in this section attempt to balance the length of raw wate r main with
the need to keep separation of wells in order to minimize well interference effects.
Alternative results are presented in the form of maps of drawdown (lowering of pressure head in the
aquifer) within the Mt. Simon-Hinckley aquifer, the Franconia-Ironton-Galesville aquifer, and the
water table (glacial drift or surficial aquifer). It is important to recognize that some drawdown does
take place in adjoining aquifers that are not being directly pumped, due to induced leakage through
separating aquitards. The drawdown maps provide a relative comparison between alternatives, based
on how much drawdown is induced – particularly near the wells. Greater amounts of drawdown
increase the likelihood of greater well interference effects and less individual well capacity.
It is also important to recognize that well efficiency is not considered in the modeling results – wells
are assumed to be 100% efficient. Wells that are not 100% efficient will have addition drawdowns
within the well (but not within the aquifer adjacent to the well) that can further reduce the total
available well yield. In general, a well is at least 90% efficient if the drawdown in the well is no
greater than 1/3 of the total available drawdown in a well (provided the well is properly des igned,
constructed, developed, and maintained).
12
3.2
Well Location Alternative Evaluation
3.2.1 Well Alternative 1
Well Alternative 1 includes five wells completed in the Mt. Simon-Hinckley aquifer, each pumping
at an average rate of 900 gpm. Spacing between wells is approximately 2,300 to 2,800 feet. The wells
are located along existing roads and the spacing of the wells is staggered. The distance from the City
limits to the farthest well (via roads) is about 2 miles.
Well locations and the predicted drawdown (feet) in the Mt. Simon-Hinckley aquifer, the FranconiaIronton-Galesville aquifer, and the water-table (surficial) aquifer caused by continuous, steady-state
pumping of the wells are shown on Figures 13, 14, and 15.
Drawdown in the wells (assuming 100% efficiency) is about 70 feet. The resulting cone of
depression in the Mt. Simon-Hinckley aquifer extends radially for about 10 miles. The cones of
depression in the overlying Franconia-Ironton-Galesville and water-table aquifers are much less
extensive, with maximum drawdown near the wells of about 10 feet.
3.2.2 Well Alternative 2
Well Alternative 2 includes five wells completed in the Mt. Simon-Hinckley aquifer, each pumping
at an average rate of 900 gpm. Spacing between wells is approximately 1,200 feet. The wells are
located along an existing north-south township road. The distance from the City limits to the line of
wells is slightly farther than 1 mile.
Well locations and the predicted drawdown (feet) in the Mt. Simon-Hinckley aquifer, the FranconiaIronton-Galesville aquifer, and the water-table (surficial) aquifer caused by continuous, steady-state
pumping of the wells are shown on Figures 16, 17, and 18.
Drawdown in the wells (assuming 100% efficiency) is about 80 to 90 feet. The resulting cone of
depression in the Mt. Simon-Hinckley aquifer extends radially for about 10 miles. The cones of
depression in the overlying Franconia-Ironton-Galesville and water-table aquifers are much less
extensive, with maximum drawdown near the wells of about 10 feet.
3.2.3 Well Alternative 3
Well Alternative 3 includes three wells completed in the Mt. Simon-Hinckley aquifer and two wells
completed in the Franconia-Ironton-Galesville aquifer, each pumping at an average rate of 900 gpm.
13
Spacing between wells is approximately 1,200 feet and the locations are identical to Well Alternative
2.. The wells are located along an existing north-south township road. The distance from the City
limits to the line of wells is slightly farther than 1 mile.
Well locations and the predicted drawdown (feet) in the Mt. Simon-Hinckley aquifer, the FranconiaIronton-Galesville aquifer, and the water-table (surficial) aquifer caused by continuous, steady-state
pumping of the wells are shown on Figures 19, 20, and 21.
Drawdown in the three Mt. Simon-Hinckley wells (assuming 100% efficiency) is about 45 to 50 feet.
Drawdown in the two Franconia-Ironton-Galesville wells (assuming 100% efficiency) is about 20
feet. The resulting cone of depression in the Mt. Simon-Hinckley aquifer extends radially for about
10 miles. The cone of depression in the overlying Franconia-Ironton-Galesville aquifer extends about
6 miles and the cone of depression in water-table aquifer extends about 2 to 3 miles from the wells.
3.3
Discussion of Well Alternatives
3.3.1 Well Capacity and Drawdown at the Wells
All three well alternatives appear to be viable – i.e., all three alternatives can supply 4,500 gpm
without excessive drawdown at the wells that would substantially affect well capacity. The predicted
drawdowns at the wells are not below the top of the pumped aquifer(s). From a well capacity point of
view, any of the three alternatives appear to be viable.
Other configurations of wells would likely work equally well. However, an important consideration
must always be well spacing. Wells should be spaced at least 1,200 feet apart to prevent excessive
drawdown at the wells.
3.3.2 Regional Drawdown Effects
The model predicts that there will be widespread drawdown in the Mt. Simon-Hinckley aquifer.
However, the pre-pumping potentiometric head in the Mt. Simon-Hinckley aquifer is about 300 feet
above the top of the aquifer. Thus, there should not be any issues of interference with other wells in
the area that are completed in the Mt. Simon-Hinckley aquifer, unless the pump setting of a particular
well is too high (in which case, the pump can be lowered by adding more drop pipe).
For Alternatives 1 and 2, the model predicts that drawdowns in the Franconia-Ironton-Galesville
aquifer and the surficial aquifer will be no more than 5 to 10 feet. Again, unless a pump is set in an
14
existing well at a very shallow depth, this drawdown should not result in any noticeable loss in a
well’s capacity. It may be necessary, as part of the Appropriations Permit approval process, to
tabulate wells in the area and identify any wells that might be susceptible to drawdown effects.
For Alternative 3, drawdown in the Franconia-Ironton-Galesville aquifer is predicted to be about 10
to 20 feet. Again, this will likely not cause capacity issues unless a well’s pump is set very shallow in
an existing well.
3.2.3 Effect of Nearby Fault System
The fault system, which is located approximately parallel to Interstate 35, was modeled in such a
manner that its effects would be conservative – i.e., it would error on the side of causing more
drawdown, rather than less. The modeling indicated that for the three alternatives, the fault has little
impact on drawdown and capacity.
As new wells are located, it will be important to identify locations that are a distance sufficiently
west of the fault system that wells are not installed in the fault (which can cause failing of open holes
and reduced yields). The three alternatives likely are located in an area where the Franconia -IrontonGalesville aquifer and the Eau Claire Formation are present above the full thickness of Mt. SimonHinckley aquifer. Caving or other hole failures should not be a problem at these locations, but test
drilling will be required to verify that the Franconia-Ironton-Galesville aquifer is present. If, during
drilling of a well, the Franconia-Ironton-Galesville units are not encountered, that location should be
abandoned and another location (likely farther to the west) should be selected.
15
4 Considerations for Future Well Siting
4.1
Test Drilling and Test Wells
The groundwater modeling presented in this report suggests that groundwater supplies are plentiful in
areas to the west of North Branch but the model relies on imperfect information in that area. As new
wells are contemplated, test drilling and test wells should be installed. The test well should verify:
1. The presence (and thickness) of the Franconia-Ironton-Galesville aquifer. If this unit is thin
(or absent) in a test hole, there is a high likelihood that the location is not west of the frac ture
zone.
2. Aquifer parameters and predictions of drawdown. The groundwater model relies on
information from regional information and the calibration process and as such, has
uncertainty associated with predictions of yield and drawdown. A pumping test should be
performed on a new test well and drawdowns should be monitored in piezometers
(monitoring wells) installed in both the Mt. Simon-Hinckley aquifer and the FranconiaIronton-Galesville aquifer. A pumping test would likely involve continuous pumping of a test
well for 96 hours and monitoring of changes in water levels in the piezometers.
Transmissivity values can be calculated from the pumping test results and if necessary, the
model can be updated to evaluate the well yields.
Test wells can be installed in a such a manner that they can be converted to production wells at a
later date. It is likely that the information from one test well can be applicable to the entire well field.
4.2
Appropriations Permits
An application for an appropriations permit from the Department of Natural Resources will likely
require some provision for aquifer testing. The DNR will also be interested in the effects of
drawdown on nearby wells. This model (perhaps with adjustments after a pumping test) would be a
good tool for addressing those types of issues. DNR staff have looked for and accepted this type of
modeling result in other permit applications.
16
4.3
Wellhead Protection Area Delineation
Preliminary wellhead protection areas (WHPAs) will need to be delineated well when a new well is
installed. Final WHPAs will need to be delineated using time-of-travel criteria. Typically, a
groundwater flow model is used. The model constructed for this study could be used for delineating
WHPAs for future wells and for the City’s existing wells.
17
References
ESI Inc., 2004, Groundwater Vistas, Version 4. Herndon, VA.
McDonald, M.G. and A.W. Harbaugh, 1988. A modular three-dimensional finite-difference groundwater flow model, USGS TWRI Chapter 6-A1, 586 p.
Morey, G.B., 1972. Petrology of Keweenawan sandstones in the subsurface of southeastern
Minnesota in Geology of Minnesota: A Centennial Volume, Sims and Morey, eds., p. 436 -449.
18
Figure 1
Uppermost Bedrock Interpreted from County Well Index Data
Figure 2
Approximate Depth to Bedrock (feet)
West
East
Figure 3
Conceptual Model of Groundwater Flow
Figure 4
Model Domain and Horizontal Grid Discretization
Figure 5
Cross Sections Through Model Depicting Vertical Discretization
Layer 2
Figure 6
Example of Zonation for Hydraulic Conductivity
Figure 7
Wall Feature, Representing Fault Boundary
Figure 8
Recharge Zones in the Model
Note: Many wells penetrate multiple layers
Figure 9
Wells in Model
Figure 10
Plot of Observed and Simulated Observations
Contour Interval = 10 feet
Figure 11
Contours of Simulated Potentiometric Head (feet, above mean sea
level)for Layer 4 (Mt. Simon-Hinckley Aquifer)
Figure 12
Relative Sensitivity of Model Calibration to Parameters
Figure 13
Well Alternative 1: Predicted Drawdown (feet) in Mt. Simon-Hinckley
Aquifer
Figure 14
Well Alternative 1: Predicted Drawdown (feet) in Franconia-IrontonGalesville Aquifer
Figure 15
Well Alternative 1: Predicted Drawdown (feet) in Water-Table Aquifer
Figure 16
Well Alternative 2: Predicted Drawdown (feet) in Mt. Simon-Hinckley
Aquifer
Figure 17
Well Alternative 2: Predicted Drawdown (feet) in Franconia-IrontonGalesville Aquifer
Figure 18
Well Alternative 2: Predicted Drawdown (feet) in Water-Table Aquifer
Figure 19
Well Alternative 3: Predicted Drawdown (feet) in Mt. Simon-Hinckley
Aquifer
Figure 20
Well Alternative 3: Predicted Drawdown (feet) in Franconia-IrontonGalesville Aquifer
Figure 21
Well Alternative 3: Predicted Drawdown (feet) in Water-Table Aquifer
Appendix F
L-Score Map
30
North Branch
North Branch Township
7
6
4
5
95
Barr Footer: ArcGIS 10.0, 2012-02-22 14:31 File: I:\Projects\23\13\1005\Maps\Reports\L_Scores.mxd User: egc
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Figure F-1
L SCORES
WHPP Part 1
North Branch Municipal
Water and Light
Chisago County, MN
Appendix G
Groundwater Model Files and GIS Shapefiles
(Electronic Format)